Methods and systems for interactive rendering of object based audio

ABSTRACT

Methods for generating an object based audio program which is renderable in a personalizable manner, e.g., to provide an immersive, perception of audio content of the program. Other embodiments include steps of delivering (e.g., broadcasting), decoding, and/or rendering such a program. Rendering of audio objects indicated by the program may provide an immersive experience. The audio content of the program may be indicative of multiple object channels (e.g., object channels indicative of user-selectable and user-configurable objects, and typically also a default set of objects which will be rendered in the absence of a selection by a user) and a bed of speaker channels. Another aspect is an audio processing unit (e.g., encoder or decoder) configured to perform, or which includes a buffer memory which stores at least one frame (or other segment) of an object based audio program (or bitstream thereof) generated in accordance with, any embodiment of the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 15/989,073 filed on May 24, 2018, now U.S. Pat. No. 10,515,644,which is a divisional application of U.S. patent application Ser. No.14/781,882 filed on Oct. 1, 2015, now U.S. Pat. No. 9,997,164, whichclaims priority to International Application No. PCT/US2014/031246 filedMar. 19, 2014, which claims the benefit of priority to U.S. ProvisionalPatent Application No. 61/807,922, filed on Apr. 3, 2013 and U.S.Provisional Patent Application No. 61/832,397, filed on Jun. 7, 2013,incorporated herein by reference.

TECHNICAL FIELD OF THE INVENTION

The invention pertains to audio signal processing, and moreparticularly, to encoding, decoding, and interactive rendering of audiodata bitstreams which include audio content (typically indicative ofspeaker channels and at least one selectable audio object channel), andmetadata which supports interactive rendering of the audio content. Someembodiments of the invention generate, decode, and/or render audio datain one of the formats known as Dolby Digital (AC-3), Dolby Digital Plus(Enhanced AC-3 or E-AC-3), or Dolby E.

BACKGROUND OF THE INVENTION

Dolby, Dolby Digital, Dolby Digital Plus, and Dolby E are trademarks ofDolby Laboratories Licensing Corporation. Dolby Laboratories providesproprietary implementations of AC-3 and E-AC-3 known as Dolby Digitaland Dolby Digital Plus, respectively.

A typical stream of audio data includes both audio content (e.g., one ormore channels of audio content) and metadata indicative of at least onecharacteristic of the audio content. For example, in an AC-3 bitstreamthere are several audio metadata parameters that are specificallyintended for use in changing the sound of the program delivered to alistening environment. One of the metadata parameters is the DIALNORMparameter, which is intended to indicate the mean level of dialogoccurring in an audio program, and is used to determine audio playbacksignal level.

Although the present invention is not limited to use with an AC-3bitstream, an E-AC-3 bitstream, or a Dolby E bitstream, for convenienceit will be described in embodiments in which it generates, decodes, orotherwise processes such a bitstream which includes loudness processingstate metadata.

An AC-3 encoded bitstream comprises metadata and one to six channels ofaudio content. The audio content is audio data that has been compressedusing perceptual audio coding. The metadata includes several audiometadata parameters that are intended for use in changing the sound of aprogram delivered to a listening environment.

Details of AC-3 (also known as Dolby Digital) coding are well known andare set forth in many published references including in ATSC StandardA52/A: Digital Audio Compression Standard (AC-3), Revision A, AdvancedTelevision Systems Committee, 20 Aug. 2001.

Details of Dolby Digital Plus (E-AC-3) coding are set forth in“Introduction to Dolby Digital Plus, an Enhancement to the Dolby DigitalCoding System,” AES Convention Paper 6196, 117^(th) AES Convention, Oct.28, 2004.

Details of Dolby E coding are set forth in “Efficient Bit Allocation,Quantization, and Coding in an Audio Distribution System”, AES Preprint5068, 107th AES Conference, August 1999 and “Professional Audio CoderOptimized for Use with Video”, AES Preprint 5033, 107th AES ConferenceAugust 1999.

Each frame of an AC-3 encoded audio bitstream contains audio content andmetadata for 1536 samples of digital audio. For a sampling rate of 48kHz, this represents 32 milliseconds of digital audio or a rate of 31.25frames per second of audio.

Each frame of an E-AC-3 encoded audio bitstream contains audio contentand metadata for 256, 512, 768 or 1536 samples of digital audio,depending on whether the frame contains one, two, three or six blocks ofaudio data respectively. For a sampling rate of 48 kHz, this represents5.333, 10.667, 16 or 32 milliseconds of digital audio respectively or arate of 189.9, 93.75, 62.5 or 31.25 frames per second of audiorespectively.

As indicated in FIG. 1, each AC-3 frame is divided into sections(segments), including: a Synchronization Information (SI) section whichcontains (as shown in FIG. 2) a synchronization word (SW) and the firstof two error correction words (CRC1); a Bitstream Information (BSI)section which contains most of the metadata; six Audio Blocks (ABO toABS) which contain data compressed audio content (and can also includemetadata); waste bits (W) which contain any unused bits left over afterthe audio content is compressed; an Auxiliary (AUX) information sectionwhich may contain more metadata; and the second of two error correctionwords (CRC2).

As indicated in FIG. 4, each E-AC-3 frame is divided into sections(segments), including: a Synchronization Information (SI) section whichcontains (as shown in FIG. 2) a synchronization word (SW); a BitstreamInformation (BSI) section which contains most of the metadata; betweenone and six Audio Blocks (ABO to ABS) which contain data compressedaudio content (and can also include metadata); waste bits (W) whichcontain any unused bits left over after the audio content is compressed;an Auxiliary (AUX) information section which may contain more metadata;and an error correction word (CRC).

In an AC-3 (or E-AC-3) bitstream there are several audio metadataparameters that are specifically intended for use in changing the soundof the program delivered to a listening environment. One of the metadataparameters is the DIALNORM parameter, which is included in the BSIsegment.

As shown in FIG. 3, the BSI segment of an AC-3 frame (or an E-AC-3frame) includes a five-bit parameter (“DIALNORM”) indicating theDIALNORM value for the program. A five-bit parameter (“DIALNORM2”)indicating the DIALNORM value for a second audio program carried in thesame AC-3 frame is included if the audio coding mode (“acmod”) of theAC-3 frame is “0”, indicating that a dual-mono or “1+1” channelconfiguration is in use.

The BSI segment also includes a flag (“addbsie”) indicating the presence(or absence) of additional bit stream information following the“addbsie” bit, a parameter (“addbsil”) indicating the length of anyadditional bit stream information following the “addbsil” value, and upto 64 bits of additional bit stream information (“addbsi”) following the“addbsil” value.

The BSI segment includes other metadata values not specifically shown inFIG. 3.

It has been proposed to include metadata of other types in audiobitstreams. For example, methods and systems for generating, decoding,and processing audio bitstreams including metadata indicative of theprocessing state (e.g., the loudness processing state) andcharacteristics (e.g., loudness) of audio content are described in PCTInternational Application Publication Number WO 2012/075246 A2, havinginternational filing date Dec. 1, 2011, and assigned to the assignee ofthe present application. This reference also describes adaptiveprocessing of the audio content of the bitstreams using the metadata,and verification of validity of the loudness processing state andloudness of audio content of the bitstreams using the metadata.

Methods for generating and rendering object based audio programs arealso known. During generation of such programs, it is typically assumedthat the loudspeakers to be employed for rendering are located inarbitrary locations in the playback environment; not necessarily in a(nominally) horizontal plane or in any other predetermined arrangementsknown at the time of program generation. Typically, metadata included inthe program indicates rendering parameters for rendering at least oneobject of the program at an apparent spatial location or along atrajectory (in a three dimensional volume), e.g., using athree-dimensional array of speakers. For example, an object channel ofthe program may have corresponding metadata indicating athree-dimensional trajectory of apparent spatial positions at which theobject (indicated by the object channel) is to be rendered. Thetrajectory may include a sequence of “floor” locations (in the plane ofa subset of speakers which are assumed to be located on the floor, or inanother horizontal plane, of the playback environment), and a sequenceof “above-floor” locations (each determined by driving a subset of thespeakers which are assumed to be located in at least one otherhorizontal plane of the playback environment). Examples of rendering ofobject based audio programs are described, for example, in PCTInternational Application No. PCT/US2001/028783, published underInternational Publication No. WO 2011/119401 A2 on Sep. 29, 2011, andassigned to the assignee of the present application.

BRIEF DESCRIPTION OF THE INVENTION

In accordance with some embodiments of the invention, an object basedaudio program (generated in accordance with the invention) is renderedso as to provide an immersive, personalizable perception of theprogram's audio content. Typically, the content is indicative of theatmosphere at (i.e., sound occurring in or at), and/or commentary on aspectator event (e.g., a soccer or rugby game, a car or motorcycle race,or another sporting event). In some embodiments, the content is notindicative of the atmosphere at or commentary on a spectator event(e.g., in some embodiments, the content is indicative of a scripted orcinematic program having multiple, selectable versions of dialog and/orother audio content). In some embodiments, the audio content of theprogram is indicative of multiple audio object channels (e.g.,indicative of user-selectable objects or object sets, and typically alsoa default set of objects to be rendered in the absence of objectselection by the user) and at least one set (sometimes referred toherein as a “bed”) of speaker channels. The bed of speaker channels maybe a conventional mix (e.g., a 5.1 channel mix) of speaker channels of atype that might be included in a conventional broadcast program whichdoes not include an object channel.

In some embodiments, object related metadata indicated by (i.e.,delivered as part of) an object based audio program provides mixinginteractivity (e.g., a large degree of mixing interactivity) on theplayback side, including by allowing an end user to select a mix ofaudio content of the program for rendering, instead of merely allowingplayback of a pre-mixed sound field. For example, a user may selectamong rendering options provided by metadata of a typical embodiment ofthe inventive program to select a subset of available object channelsfor rendering, and optionally also the playback level of at least oneaudio object (sound source) indicated by the object channel(s) to berendered. The spatial location at which each selected sound source isrendered may be predetermined by metadata included in the program, butin some embodiments can be selected by the user (e.g., subject topredetermined rules or constraints). In some embodiments, metadataincluded in the program allows user selection from among a menu ofrendering options (e.g., a small number of rendering options, forexample, a “home team crowd noise” object, a “home team crowd noise” anda “home team commentary” object set, an “away team crowd noise” object,and an “away team crowd noise” and “away team commentary” object set).The menu may be presented to the user by a user interface of acontroller. The controller is typically coupled (e.g., by a wirelesslink) to a set top device (or other device, e.g., a TV, AVR, tablet, orphone) which is configured to decode and render (at least partially) theobject based program. In some other embodiments, metadata included inthe program otherwise allows user selection from among a set of optionsas to which object(s) indicated by the object channels should berendered, and as to how the object(s) to be rendered should beconfigured.

In a class of embodiments, the invention is a method of generating anobject based audio program (e.g., including by encoding audio content togenerate the program) such that the program is renderable in apersonalizable manner to provide an immersive, perception of audiocontent of the program. Other embodiments include steps of delivering(e.g., broadcasting), decoding, and/or rendering such a program.Rendering of audio objects indicated by (included in) the program canprovide an immersive experience (e.g., when the playback system includesa three-dimensional array of speakers, or even when the playback systemincludes a nominally two-dimensional array of speakers).

Typically, the audio content of the program is indicative of multipleaudio objects (e.g., user-selectable objects, and typically also adefault set of objects which will be rendered in the absence of aselection by the user) and a set (“bed”) of speaker channels. In someembodiments, a consumer uses a controller (which implements a userinterface) to select object channel content of the program (andcorresponding rendering parameters), but the controller does not providean option for the user to select speaker channel content of the program(i.e., individual speaker channels of the bed).

In some embodiments, the object based audio program is an encoded (e.g.,compressed) audio bitstream (sometimes referred to herein as a “mainmix”) indicative of at least some (i.e., at least a part) of theprogram's audio content (e.g., a bed of speaker channels and at leastsome of the program's object channels) and object related metadata, andoptionally also at least one additional bitstream or file (sometimesreferred to herein as a “side mix”) indicative of some of the program'saudio content (e.g., at least some of the object channels) and/or objectrelated metadata.

In some embodiments, object related metadata of the program includesdurable metadata (e.g., durable metadata and non-durable metadata). Forexample, the object related metadata may include non-durable metadata(e.g., a default level and/or rendering position or trajectory, for auser-selectable object) which can be changed at at least one point inthe broadcast chain (from the content creation facility to theconsumer's user interface) and durable metadata which is not intended tobe changeable (or cannot be changed) after initial generation of theprogram (typically, in a content creation facility). Examples of durablemetadata include an object ID for each user-selectable object or otherobject or set of objects of the program, and synchronization words(e.g., time codes) indicative of timing of each user-selectable object,or other object, relative to audio content of the bed of speakerchannels or other elements of the program. Durable metadata is typicallypreserved throughout the entire broadcast chain from content creationfacility to user interface, throughout the entire duration of abroadcast of the program or even also during re-broadcasts of theprogram. In some embodiments, the audio content (and associatedmetadata) of at least one user-selectable object is sent in a main mixof the object based audio program, and at least some durable metadata(e.g., time codes) and optionally also audio content (and associatedmetadata) of at least one other object is sent in a side mix of theprogram.

Durable metadata in some embodiments of the inventive object based audioprogram is employed to preserve (e.g., even after broadcast of theprogram) a user selected mix of object content and bed (speaker channel)content. For example, this may provide the selected mix as a default mixeach time the user a program of a specific type (e.g., any soccer game)or each time the user watches any program (of any type), until the userchanges his/her selection. For example, during broadcast of a firstprogram, the user may select a mix including an object having a durableID (e.g., an object identified as a “home team crowd noise” object), andthen each time the user watches (and listens to) another program (whichincludes an object having the same durable ID), the playback system willautomatically render the program with the same mix, until the userchanges the mix selection. Durable, object related metadata in someembodiments of the inventive object based audio program may causerendering of some objects to be mandatory (e.g., despite a user's desireto defeat such rendering) during an entire program.

In some embodiments, object related metadata provides a default mix ofobject content and bed (speaker channel) content, with default renderingparameters (e.g., default spatial locations of rendered objects).

In some embodiments, object related metadata provides a set ofselectable “preset” mixes of objects and “bed” speaker channel content,each preset mix having a predetermined set of rendering parameters(e.g., spatial locations of rendered objects). These may be presented bya user interface of the playback system as a limited menu or palette ofavailable mixes. Each preset mix (and/or each selectable object) mayhave a durable ID (e g., name, label or logo), and an indication of suchID is typically displayable by a user interface of the playback system(e.g., on the screen of an iPad or other controller). For example, theremay be a selectable “home team” mix with an ID (e.g., a team logo) thatis durable, regardless of changes (e.g., made by the broadcaster) todetails of the audio content or nondurable metadata of each object ofthe preset mix.

In some embodiments, object related metadata of a program (or apreconfiguration of the playback or rendering system, not indicated bymetadata delivered with the program) provides constraints or conditionson selectable mixes of objects and bed (speaker channel) content. Forexample, if digital rights management (DRM) is employed, a DRM hierarchymay be implemented to allow customers to have “tiered” access to a setof audio objects included in an object based audio program. If acustomer pays more money (e.g., to the broadcaster), the customer may beauthorized to decode and select (and hear) more audio objects of theprogram. For another example, object related metadata may provideconstraints on user selection of objects (e.g., if both a “home teamcrowd noise” object and a “home team announcer” object are selected, themetadata ensures that these two objects are rendered with predeterminedrelative spatial locations). The constraints may be determined (at leastin part) by data (e.g., user-entered data) regarding the playbacksystem. For example, if the playback system is a stereo system(including only two speakers), the system's object processing subsystemmay be configured to prevent user selection of mixes (identified byobject related metadata) that cannot be rendered with adequate spatialresolution by only two speakers. For another example, some deliveredobjects may be removed from the category of selectable objects for legal(e.g., DRM) reasons or other reasons (e.g. based on bandwidth of thedelivery channel) indicated by object related metadata (and/or otherdata entered to the playback system). The user may pay the contentcreator or broadcaster for more bandwidth, and as a result may beallowed to select from a larger menu of selectable objects and/orbed/object mixes.

In some embodiments, the invention implements rule based object channelselection, in which at least one predetermined rule determines whichobject channel(s) of an object based audio program are rendered (e.g.,with a bed of speaker channels). Typically, the user specifies at leastone rule for object channel selection (e.g., by selecting from a menu ofavailable rules presented by a user interface of a playback systemcontroller), and the playback system applies each such rule to determinewhich object channel(s) of an object based audio program should beincluded in the mix of channels to be rendered. The playback system maydetermine from object related metadata in the program which objectchannel(s) of the program satisfy the predetermined rule(s).

In some embodiments, the inventive object based audio program includes aset of bitstreams (multiple bitstreams, which may be referred to as“substreams”) which are generated and transmitted in parallel.Typically, multiple decoders are employed to decode them (e.g., theprogram includes multiple E-AC-3 substreams and the playback systememploys multiple E-AC-3 decoders to decode the substreams). Typically,each substream includes a different subset of a full set of objectchannels and corresponding object related metadata, and at least onesubstream includes a bed of speaker channels. Each substream preferablyincludes synchronization words (e.g., time codes) to allow thesubstreams to be synchronized or time aligned with each other. Forexample, in each substream, each container which includes object channelcontent and object related metadata includes a unique ID or time stamp.

For another example, a set of N of the inventive Dolby E bitstreams isgenerated and transmitted in parallel. Each such Dolby E bitstreamcomprises a sequence of bursts. Each burst may carry speaker channelaudio content (a “bed” of speaker channels) and a subset of a fullobject channel set (which may be a large set) of the inventive objectchannels and object related metadata (i.e., each burst may indicate someobject channels of the full object channel set and corresponding objectrelated metadata). Each bitstream in the set includes synchronizationwords (e.g., time codes) to allow the bitstreams in the set to besynchronized or time aligned with each other. For example, in eachbitstream, each container including object channel content and objectrelated metadata could include a unique ID or time stamp to allow thebitstreams in the set to be synchronized or time aligned with eachother.

Some embodiments of the invention (e.g., some embodiments of theinventive playback system) implement distributed rendering. For example,selected object channels (and corresponding object related metadata) ofa program are passed on (with a decoded bed of speaker channels) from aset top device (STB) to a downstream device (e.g., an AVR or soundbar)configured to render a mix of the object channels and the bed of speakerchannels. The STB may partially render the audio and the downstreamdevice may complete the rendering (e.g., by generating speaker feeds fordriving a specific top tier of speakers (e.g., ceiling speakers) toplace an audio object in a specific apparent source position, where theSTB's output merely indicates that the object can be rendered in someunspecified way in some unspecified top tier of speakers). For example,the STB may not have knowledge of the specific organization of thespeakers of the playback system, but the downstream device (e.g., AVR orsoundbar) may have such knowledge.

In some embodiments, the object based audio program is or includes atleast one AC-3 (or E-AC-3) bitstream, and each container of the programwhich includes object channel content (and/or object related metadata)is included in an auxdata field (e.g., the AUX segment shown in FIG. 1or FIG. 4) at the end of a frame of the bitstream, or in a “skip fields”segment of the bitstream. In some such embodiments, each frame of theAC-3 or E-AC-3 bitstream includes one or two metadata containers. Onecontainer can be included in the Aux field of the frame, and anothercontainer can be included in the addbsi field of the frame. Eachcontainer has a core header and includes (or is associated with) one ormore payloads. One such payload (of or associated with a containerincluded in the Aux field) may be a set of audio samples of each of oneor more of the inventive object channels (related to the bed of speakerchannels which is also indicated by the program) and the object relatedmetadata associated with each object channel. The core header of eachcontainer typically includes at least one ID value indicating the typeof payload(s) included in or associated with the container; substreamassociation indications (indicating which substreams the core header isassociated with); and protection bits. Typically, each payload has itsown header (or “payload identifier”). Object level metadata may becarried in each substream which is an object channel.

In other embodiments, the object based audio program is or includes abitstream which is not an AC-3 bitstream or an E-AC-3 bitstream. In someembodiments, the object based audio program is or includes at least oneDolby E bitstream, and the object channel content and object relatedmetadata of the program (e.g., each container of the program whichincludes object channel content and/or object related metadata) isincluded in bit locations of the Dolby E bitstream that conventionallydo not carry useful information. Each burst of a Dolby E bitstreamoccupies a time period equivalent to that of a corresponding videoframe. The object channels (and object related metadata) may be includedin the guard bands between Dolby E bursts and/or in the unused bitlocations within each of data structures (each having the format of anAES3 frame) within each Dolby E burst. For example, each guard bandconsists of a sequence of segments (e.g., 100 segments), each of thefirst X segments (e.g., X=20) of each guard band includes the objectchannels and object related metadata, and each of the remaining segmentsof said each guard band may include a guard band symbol. In someembodiments, the object channels and object related metadata of Dolby Ebitstreams are included in metadata containers. Each container has acore header and includes (or is associated with) one or more payloads.One such payload (of or associated with a container included in the Auxfield) may be a set of audio samples of each of one or more of theinventive object channels (related to the bed of speaker channels whichis also indicated by the program) and the object related metadataassociated with each object channel. The core header of each containertypically includes at least one ID value indicating the type ofpayload(s) included in or associated with the container; substreamassociation indications (indicating which substreams the core header isassociated with); and protection bits. Typically, each payload has itsown header (or “payload identifier”). Object level metadata may becarried in each substream which is an object channel.

In some embodiments, a broadcast facility (e.g., an encoding system insuch a facility) generates multiple audio representations (object basedaudio programs) based on captured sound (e.g., a 5.1 flattened mix, aninternational mix, a domestic mix). For example, the bed of speakerchannels, and/or the menu of selectable objects (or selectable ornonselectable rendering parameters for rendering and mixing objects) ofthe programs may differ from program to program.

In some embodiments, the object based audio program is decodable and thespeaker channel content thereof is renderable by a legacy decoder andlegacy rendering system (which is not configured to parse the inventiveobject channels and object related metadata). The same program may berendered in accordance with some embodiments of the invention by a settop device (or other decoding and rendering system, e.g., a TV, AVR,tablet, or phone) which is configured (in accordance with an embodimentof the invention) to parse the inventive object channels and objectrelated metadata and render a mix of speaker channel and object channelcontent indicated by the program.

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance withsome embodiments of the invention includes at least one bed of speakerchannels, at least one object channel, and metadata indicative of alayered graph (sometimes referred to as a layered “mix graph”)indicative of selectable mixes (e.g., all selectable mixes) of thespeaker channels and object channel(s). For example, the mix graph isindicative of each rule applicable to selection of subsets of thespeaker and object channels. Typically, an encoded audio bitstream isindicative of at least some (i.e., at least a part) of the program'saudio content (e.g., a bed of speaker channels and at least some of theprogram's object channels) and object related metadata (including themetadata indicative of the mix graph,) and optionally also at least oneadditional encoded audio bitstream or file is indicative of some of theprogram's audio content and/or object related metadata.

The layered mix graph is indicative of nodes (each of which may beindicative of a selectable channel or set of channels, or a category ofselectable channels or set of channels) and connections between thenodes (e.g., control interfaces to the nodes and/or rules for selectingchannels), and includes essential data (a “base” layer) and optional(i.e., optionally omitted) data (at least one “extension” layer).Typically, the layered mix graph is included in one of the encoded audiobitstream(s) indicative of the program, and can be assessed by graphtraversal (e.g., implemented by a playback system) to determine adefault mix of channels and options for modifying the default mix.

Where the mix graph is representable as a tree graph, the base layer canbe a branch (or two or more branches) of the tree graph, and eachextension layer can be another branch (or another set of two or morebranches) of the tree graph. For example, one branch of the tree graph(indicated by the base layer) may be indicative of selectable channelsand sets of channels that are available to all end users, and anotherbranch of the tree graph (indicated by an extension layer) may beindicative of additional selectable channels and/or sets of channelsthat are available only to some end users (e.g., such an extension layermay be provided only to end users authorized to use it).

Typically the base layer contains (is indicative of) the graph structureand control interfaces to the nodes of the graph (e.g., panning, andgain control interfaces). The base layer is necessary for mapping anyuser interaction to the decoding/rendering process.

Each extension layer contains (is indicative of) an extension to thebase layer. The extensions are not immediately necessary for mappinguser interaction to the decoding process and hence can be transmitted ata slower rate and/or delayed, or omitted.

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance someembodiments of the invention includes at least one bed of speakerchannels, at least one object channel, and metadata indicative of a mixgraph (which may or may not be a layered mix graph) indicative ofselectable mixes (e.g., all selectable mixes) of the speaker channelsand the object channel(s). An encoded audio bitstream (e.g., a Dolby Eor E-AC-3 bitstream) is indicative of at least a portion of the program,and metadata indicative of the mix graph (and typically also theselectable object and/or speaker channels) is included in every frame ofthe bitstream (or in each frame of a subset of the frames of thebitstream). For example, each frame may include at least one metadatasegment and at least one audio data segment, and the mix graph may beincluded in at least one metadata segment of each frame. Each metadatasegment (which may be referred to as a “container”) may have a formatwhich includes a metadata segment header (and optionally also otherelements), and one or more metadata payloads following the metadatasegment header. Each metadata payload is itself identified by a payloadheader. The mix graph, if present in a metadata segment, is included inone of the metadata payloads of the metadata segment.

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance withsome embodiments of the invention includes at least two beds of speakerchannels, at least one object channel, and metadata indicative of a mixgraph (which may or may not be a layered mix graph). The mix graph isindicative of selectable mixes (e.g., all selectable mixes) of thespeaker channels and the object channel(s), and includes at least one“bed mix” node. Each “bed mix” node defines a predetermined mix ofspeaker channel beds, and thus indicates or implements a predeterminedset of mixing rules (optionally with user-selectable parameters) formixing speaker channels of two or more speaker beds of the program.

In another class of embodiments, an object based audio program generated(or transmitted, stored, buffered, decoded, rendered, or otherwiseprocessed) in accordance with the invention includes substreams, and thesubstreams are indicative of at least one bed of speaker channels, atleast one object channel, and object related metadata. The objectrelated metadata includes “substream” metadata (indicative of substreamstructure of the program and/or the manner in which the substreamsshould be decoded) and typically also a mix graph indicative ofselectable mixes (e.g., all selectable mixes) of the speaker channelsand the object channel(s). The substream metadata may be indicative ofwhich substreams of the program should be decoded independently of othersubstreams of the program, and which substreams of the program should bedecoded in association with at least one other substream of the program.

In an example embodiment, an object based audio program includes atleast one bed of speaker channels, at least one object channel, andmetadata. The metadata includes “substream” metadata (indicative ofsubstream structure of audio content of the program and/or the manner inwhich substreams of audio content of the program should be decoded) andtypically also a mix graph indicative of selectable mixes of the speakerchannels and the object channel(s). The audio program associated with asoccer game. An encoded audio bitstream (e.g., an E-AC-3 bitstream) isindicative of the program's audio content and metadata. The audiocontent of the program (and thus of the bitstream) includes at least twoindependent substreams. One independent substream is indicative of a 5.1speaker channel bed indicative of neutral crowd noise at the soccergame. Another independent substream is indicative of a 2.0 channel “TeamA” bed indicative of sound from the portion of the game crowd biasedtoward one team (“Team A”), a 2.0 channel “Team B” bed indicative ofsound from the portion of the game crowd biased toward the other team(“Team B”), and a monophonic object channel indicative of commentary onthe game. Substream metadata of the bitstream indicates that duringdecoding, coupling should be “off” between each pair of the independentsubstreams (so that each independent substream is decoded independentlyof the other independent substreams), and substream metadata of thebitstream indicates the program channels within each substream for whichcoupling should be “on” (so that these channels are not decodedindependently of each other) or “off” (so that these channels aredecoded independently of each other). For example, the substreammetadata indicates that coupling should be “on” internal to each of thetwo stereo speaker channel beds (the 2.0 channel “Team A” bed and the2.0 channel “Team B” bed) of the second substream but disabled acrossthe speaker channel beds of the second substream and between themonophonic object channel and each of the speaker channel beds of thesecond substream (to cause the monophonic object channel and the speakerchannel beds to be decoded independently of each other). Similarly, thesubstream metadata indicates that coupling should be “on” internal tothe 5.1 speaker channel bed of the first substream I0.

Another aspect of the invention is an audio processing unit (APU)configured to perform any embodiment of the inventive method. In anotherclass of embodiments, the invention is an APU including a buffer memory(buffer) which stores (e.g., in a non-transitory manner) at least oneframe or other segment (including audio content of a bed of speakerchannels and of object channels, and object related metadata) of anobject based audio program which has been generated by any embodiment ofthe inventive method. Examples of APUs include, but are not limited toencoders (e.g., transcoders), decoders, codecs, pre-processing systems(pre-processors), post-processing systems (post-processors), audiobitstream processing systems, and combinations of such elements.

Aspects of the invention include a system or device configured (e.g.,programmed) to perform any embodiment of the inventive method, and acomputer readable medium (e.g., a disc) which stores code (e.g., in anon-transitory manner) for implementing any embodiment of the inventivemethod or steps thereof. For example, the inventive system can be orinclude a programmable general purpose processor, digital signalprocessor, or microprocessor, programmed with software or firmwareand/or otherwise configured to perform any of a variety of operations ondata, including an embodiment of the inventive method or steps thereof.Such a general purpose processor may be or include a computer systemincluding an input device, a memory, and processing circuitry programmed(and/or otherwise configured) to perform an embodiment of the inventivemethod (or steps thereof) in response to data asserted thereto.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an AC-3 frame, including the segments into whichit is divided.

FIG. 2 is a diagram of the Synchronization Information (SI) segment ofan AC-3 frame, including segments into which it is divided.

FIG. 3 is a diagram of the Bitstream Information (BSI) segment of anAC-3 frame, including segments into which it is divided.

FIG. 4 is a diagram of an E-AC-3 frame, including segments into which itis divided.

FIG. 5 is a block diagram of an embodiment of a system which may beconfigured to perform an embodiment of the inventive method.

FIG. 6 is a block diagram of a playback system configured in accordancewith an embodiment of the invention.

FIG. 7 is a block diagram of a playback system configured in accordancewith another embodiment of the invention.

FIG. 8 is a block diagram of a broadcast system configured to generatean object based audio program (and a corresponding video program) inaccordance with an embodiment of the invention.

FIG. 9 is a diagram of relationships between object channels of anembodiment of the inventive program, indicating which subsets of theobject channels are selectable by a user.

FIG. 10 is a block diagram of a system which implements an embodiment ofthe invention.

FIG. 11 is a diagram of content of an object based audio programgenerated in accordance with an embodiment of the invention.

NOTATION AND NOMENCLATURE

Throughout this disclosure, including in the claims, the expressionperforming an operation “on” a signal or data (e.g., filtering, scaling,transforming, or applying gain to, the signal or data) is used in abroad sense to denote performing the operation directly on the signal ordata, or on a processed version of the signal or data (e.g., on aversion of the signal that has undergone preliminary filtering orpre-processing prior to performance of the operation thereon).

Throughout this disclosure including in the claims, the expression“system” is used in a broad sense to denote a device, system, orsubsystem. For example, a subsystem that implements a decoder may bereferred to as a decoder system, and a system including such a subsystem(e.g., a system that generates X output signals in response to multipleinputs, in which the subsystem generates M of the inputs and the otherX-M inputs are received from an external source) may also be referred toas a decoder system.

Throughout this disclosure including in the claims, the term “processor”is used in a broad sense to denote a system or device programmable orotherwise configurable (e.g., with software or firmware) to performoperations on data (e.g., audio, or video or other image data). Examplesof processors include a field-programmable gate array (or otherconfigurable integrated circuit or chip set), a digital signal processorprogrammed and/or otherwise configured to perform pipelined processingon audio or other sound data, a programmable general purpose processoror computer, and a programmable microprocessor chip or chip set.

Throughout this disclosure including in the claims, the expression“audio video receiver” (or “AVR”) denotes a receiver in a class ofconsumer electronics equipment used to control playback of audio andvideo content, for example in a home theater.

Throughout this disclosure including in the claims, the expression“soundbar” denotes a device which is a type of consumer electronicsequipment (typically installed in a home theater system), and whichincludes at least one speaker (typically, at least two speakers) and asubsystem for rendering audio for playback by each included speaker (orfor playback by each included speaker and at least one additionalspeaker external to the soundbar).

Throughout this disclosure including in the claims, the expressions“audio processor” and “audio processing unit” are used interchangeably,and in a broad sense, to denote a system configured to process audiodata. Examples of audio processing units include, but are not limited toencoders (e.g., transcoders), decoders, codecs, pre-processing systems,post-processing systems, and bitstream processing systems (sometimesreferred to as bitstream processing tools).

Throughout this disclosure including in the claims, the expression“metadata” (e.g., as in the expression “processing state metadata”)refers to separate and different data from corresponding audio data(audio content of a bitstream which also includes metadata). Metadata isassociated with audio data, and indicates at least one feature orcharacteristic of the audio data (e.g., what type(s) of processing havealready been performed, or should be performed, on the audio data, orthe trajectory of an object indicated by the audio data). Theassociation of the metadata with the audio data is time-synchronous.Thus, present (most recently received or updated) metadata may indicatethat the corresponding audio data contemporaneously has an indicatedfeature and/or comprises the results of an indicated type of audio dataprocessing.

Throughout this disclosure including in the claims, the term “couples”or “coupled” is used to mean either a direct or indirect connection.Thus, if a first device couples to a second device, that connection maybe through a direct connection, or through an indirect connection viaother devices and connections.

Throughout this disclosure including in the claims, the followingexpressions have the following definitions:

speaker and loudspeaker are used synonymously to denote anysound-emitting transducer. This definition includes loudspeakersimplemented as multiple transducers (e.g., woofer and tweeter);

speaker feed: an audio signal to be applied directly to a loudspeaker,or an audio signal that is to be applied to an amplifier and loudspeakerin series;

channel (or “audio channel”): a monophonic audio signal. Such a signalcan typically be rendered in such a way as to be equivalent toapplication of the signal directly to a loudspeaker at a desired ornominal position. The desired position can be static, as is typicallythe case with physical loudspeakers, or dynamic;

audio program: a set of one or more audio channels (at least one speakerchannel and/or at least one object channel) and optionally alsoassociated metadata (e.g., metadata that describes a desired spatialaudio presentation);

speaker channel (or “speaker-feed channel”): an audio channel that isassociated with a named loudspeaker (at a desired or nominal position),or with a named speaker zone within a defined speaker configuration. Aspeaker channel is rendered in such a way as to be equivalent toapplication of the audio signal directly to the named loudspeaker (atthe desired or nominal position) or to a speaker in the named speakerzone;

object channel: an audio channel indicative of sound emitted by an audiosource (sometimes referred to as an audio “object”). Typically, anobject channel determines a parametric audio source description (e.g.,metadata indicative of the parametric audio source description isincluded in or provided with the object channel). The source descriptionmay determine sound emitted by the source (as a function of time), theapparent position (e.g., 3D spatial coordinates) of the source as afunction of time, and optionally at least one additional parameter(e.g., apparent source size or width) characterizing the source;

object based audio program: an audio program comprising a set of one ormore object channels (and optionally also comprising at least onespeaker channel) and optionally also associated metadata (e.g., metadataindicative of a trajectory of an audio object which emits soundindicated by an object channel, or metadata otherwise indicative of adesired spatial audio presentation of sound indicated by an objectchannel, or metadata indicative of an identification of at least oneaudio object which is a source of sound indicated by an object channel);and

render: the process of converting an audio program into one or morespeaker feeds, or the process of converting an audio program into one ormore speaker feeds and converting the speaker feed(s) to sound using oneor more loudspeakers (in the latter case, the rendering is sometimesreferred to herein as rendering “by” the loudspeaker(s)). An audiochannel can be trivially rendered (“at” a desired position) by applyingthe signal directly to a physical loudspeaker at the desired position,or one or more audio channels can be rendered using one of a variety ofvirtualization techniques designed to be substantially equivalent (forthe listener) to such trivial rendering. In this latter case, each audiochannel may be converted to one or more speaker feeds to be applied toloudspeaker(s) in known locations, which are in general different fromthe desired position, such that sound emitted by the loudspeaker(s) inresponse to the feed(s) will be perceived as emitting from the desiredposition. Examples of such virtualization techniques include binauralrendering via headphones (e.g., using Dolby Headphone processing whichsimulates up to 7.1 channels of surround sound for the headphone wearer)and wave field synthesis.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

In some embodiments, the invention is a method and system for deliveringobject based audio for broadcast, which includes an improved renderingprocess (in which the consumer can interactively control aspects of therendered program), and typically also an improved live broadcastworkflow and/or an improved post production workflow.

FIG. 5 is a block diagram of an example of an audio processing chain (anaudio data processing system), in which one or more of the elements ofthe system may be configured in accordance with an embodiment of thepresent invention. The system includes the followings elements, coupledtogether as shown: capture unit 1, production unit 3 (which includes anencoding subsystem), delivery subsystem 5, decoder 7, object processingsubsystem 9, controller 10, and rendering subsystem 11. In variations onthe system shown, one or more of the elements are omitted, or additionalaudio data processing units are included. Typically, elements 7, 9, 10,and 11 are included in a playback system (e.g., the end user's hometheater system).

Capture unit 1 is typically configured to generate PCM (time-domain)samples comprising audio content, and to output the PCM samples. Thesamples may be indicative of multiple streams of audio captured bymicrophones (e.g., at a sporting event or other spectator event).Production unit 3, typically operated by a broadcaster, is configured toaccept the PCM samples as input and to output an object based audioprogram indicative of the audio content. The program typically is orincludes an encoded (e.g., compressed) audio bitstream (sometimesreferred to herein as a “main mix”) indicative of at least some of theaudio content, and optionally also at least one additional bitstream orfile (sometimes referred to herein as a “side mix”) indicative of someof the audio content. The data of the encoded bitstream (and of eachgenerated side mix, if any is generated) that are indicative of theaudio content are sometimes referred to herein as “audio data.” If theencoding subsystem of production unit 3 is configured in accordance witha typical embodiment of the present invention, the object based audioprogram output from unit 3 is indicative of (i.e., includes) multiplespeaker channels (a “bed” of speaker channels) of audio data, multipleobject channels of audio data, and object related metadata. The programmay include a main mix which in turn includes audio content indicativeof a bed of speaker channels, audio content indicative of at least oneuser-selectable object channel (and optional at least one other objectchannel), and object related metadata associated with each objectchannel. The program may also include at least one side mix whichincludes audio content indicative of at least one other object channel(e.g., at least one user-selectable object channel) and/or objectrelated metadata. The object related metadata of the program may includedurable metadata (to be described below). The program (e.g., the mainmix thereof) may be indicative of one or beds, or no bed, of speakerchannels. For example, the main mix may be indicative of two or morebeds of speaker channels (e.g., a 5.1 channel neutral crowd noise bed, a2.0 channel home team crowd noise bed, and a 2.0 away team crowd noisebed), including at least one user-selectable bed (which can be selectedusing the same user interface employed for user selection of objectchannel content or configuration) and a default bed (which will berendered in the absence of user selection of another bed). The defaultbed may be determined by data indicative of configuration (e.g., theinitial configuration) of the speaker set of the playback system, andoptionally the user may select another bed to be rendered in place ofthe default bed.

Delivery subsystem 5 of FIG. 5 is configured to store and/or transmit(e.g., broadcast) the program generated by unit 3 (e.g., main mix andeach side mix thereof, if any side mix is generated).

In some embodiments, subsystem 5 implements delivery of an object basedaudio program, in which audio objects (and at least some correspondingobject related metadata) are sent over a broadcast system (in a main mixof the program, indicated by an audio bitstream which is broadcast), andat least some object related metadata (e.g., metadata indicative ofconstraints on rendering or mixing of object channels of the program)and/or at least one object channel of the program, are delivered (as a“side mix” of the main mix) in another manner (e.g., the side mix issent to a specific end user by an Internet Protocol or “IP” network).Alternatively, the end user's decoding and/or rendering system ispreconfigured with at least some object related metadata (e.g., metadataindicative of constraints on rendering or mixing of audio objects of anembodiment of the inventive object based audio program), and such objectrelated metadata is not broadcast or otherwise delivered (by subsystem5) with the corresponding object channels (either in a main mix or sidemix of the object based audio program).

In some embodiments, timing and synchronization of portions or elementsof an object based audio program which are delivered over separate paths(e.g., a main mix which is broadcast over a broadcast system, andrelated metadata which are sent as a side mix over an IP network), isprovided by synchronization words (e.g., time codes) that are sent overall the delivery paths (e.g., in a main mix and each corresponding sidemix).

With reference again to FIG. 5, decoder 7 accepts (receives or reads)the program (or at least one bitstream or other element of the program)delivered by delivery subsystem 5, and decodes the program (or eachaccepted element thereof). In some embodiments of the invention, theprogram includes a main mix (an encoded bitstream, e.g., an AC-3 orE-AC-3 encoded bitstream) and at least one side mix of the main mix, anddecoder 7 receives and decodes the main mix (and optionally also atleast one side mix). Optionally, at least one side mix of the program(e.g., an object channel) which does not need to be decoded is deliveredby subsystem 5 directly to object processing subsystem 9. If decoder 7is configured in accordance with a typical embodiment of the presentinvention, the output of decoder 7 in typical operation includes thefollowing:

streams of audio samples indicative of the program's bed of speakerchannels; and

streams of audio samples indicative of object channels (e.g.,user-selectable audio object channels) of the program and correspondingstreams of object related metadata.

Object processing subsystem 9 is coupled to receive (from decoder 7)decoded speaker channels, object channels, and object related metadataof the delivered program, and optionally also at least one side mix(indicative of at least one other object channel) of the program. Forexample, subsystem 9 may receive (from decoder 7) audio samples of theprogram's speaker channels and of at least one object channel of theprogram, and object related metadata of the program, and may alsoreceive (from delivery subsystem 5) audio samples of at least one otherobject channel of the program (which have not undergone decoding indecoder 7).

Subsystem 9 is coupled and configured to output to rendering subsystem11 a selected subset of the full set of object channels indicated by theprogram, and corresponding object related metadata. Subsystem 9 istypically also configured to pass through unchanged (to subsystem 11)the decoded speaker channels from decoder 7, and may be configured toprocess at least some of the object channels (and/or metadata) assertedthereto to generate the object channels and metadata it asserts tosubsystem 11.

The object channel selection performed by subsystem 9 is typicallydetermined by user selection(s) (as indicated by control data assertedto subsystem 9 from controller 10) and/or rules (e.g., indicative ofconditions and/or constraints) which subsystem 9 has been programmed orotherwise configured to implement. Such rules may be determined byobject related metadata of the program and/or by other data (e.g., dataindicative of the capabilities and organization of the playback system'sspeaker array) asserted to subsystem 9 (e.g., from controller 10 oranother external source) and/or by preconfiguring (e.g., programming)subsystem 9. In some embodiments, controller 10 (via a user interfaceimplemented by controller 10) provides (e.g., displays on a touchscreen) to the user a menu or palette of selectable “preset” mixes ofobjects and “bed” speaker channel content. The selectable preset mixesmay be determined by object related metadata of the program andtypically also by rules implemented by subsystem 9 (e.g., rules whichsubsystem 9 has been preconfigured to implement). The user selects fromamong the selectable mixes by entering commands to controller 10 (e.g.,by actuating a touch screen thereof), and in response, controller 10asserts corresponding control data to subsystem 9.

Rendering subsystem 11 of FIG. 5 is configured to render the audiocontent determined by the output of subsystem 9, for playback by thespeakers (not shown) of the playback system. Subsystem 11 is configuredto map, to the available speaker channels, the audio objects determinedby the object channels selected by object processing subsystem 9 (e.g.,default objects, and/or user-selected objects which have been selectedas a result of user interaction using controller 10), using renderingparameters output from subsystem 9 (e.g., user-selected and/or defaultvalues of spatial position and level) which are associated with eachselected object. At least some of the rendering parameters aredetermined by the object related metadata output from subsystem 9.Rendering system 11 also receives the bed of speaker channels passedthrough by subsystem 9. Typically, subsystem 11 is an intelligent mixer,and is configured to determine speaker feeds for the available speakersincluding by mapping one or more selected (e.g., default-selected)objects to each of a number of individual speaker channels, and mixingthe objects with “bed” audio content indicated by each correspondingspeaker channel of the program's speaker channel bed.

FIG. 6 is a block diagram of an embodiment of the inventive playbacksystem which includes decoder 20, object processing subsystem 22,spatial rendering subsystem 25, controller 23 (which implements a userinterface), and optionally also digital audio processing subsystems 25,26, and 27, coupled as shown. In some implementations, elements 20, 22,24, 25, 26, 27, 29, 31, and 33 of the FIG. 6 system are implemented as aset top device.

In the system of FIG. 6, decoder 20 is configured to receive and decodean encoded signal indicative of object based audio program (or of a mainmix of object based audio program). The program (e.g., the program'smain mix) is indicative of audio content including at least two speakerchannels (i.e., a “bed” of at least two speaker channels). The programis also indicative of at least one user-selectable object channel (andoptionally at least one other object channel) and object relatedmetadata corresponding to each object channel. Each object channel isindicative of an audio object, and thus object channels are sometimesreferred to herein as “objects” for convenience. In an embodiment, theprogram is (or includes main mix which is) an AC-3 or E-AC-3 bitstream,indicative of audio objects, object-related metadata, and a bed ofspeaker channels. Typically, the individual audio objects are eithermono or stereo coded (i.e., each object channel is indicative of a leftor right channel of an object, or is a monophonic channel indicative ofan object), the bed is a traditional 5.1 mix, and decoder 20 may beconfigured to decode up to 16 channels of audio content (including thesix speaker channels of the bed, and up to ten object channels)simultaneously. The incoming E-AC-3 (or AC-3) bitstream may beindicative of more than ten audio objects, since not all of them mayneed to be decoded to achieve a specific mix.

In some embodiments of the inventive playback system, each frame of anincoming E-AC-3 (or AC-3) encoded bitstream includes one or two metadata“containers.” The incoming bitstream is indicative of an object basedaudio program, or a main mix of such a program, and the speaker channelsof the program are organized as is the audio content of a conventionalE-AC-3 (or AC-3) bitstream. One container can be included in the Auxfield of the frame, and another container can be included in the addbsifield of the frame. Each container has a core header and includes (or isassociated with) one or more payloads. One such payload (of orassociated with a container included in the Aux field) may be a set ofaudio samples of each of one or more of the inventive object channels(related to the bed of speaker channels which is also indicated by theprogram) and object related metadata associated with each object channelIn such a payload, the samples of some or all of the object channels(and associated metadata) may be organized as standard E-AC-3 (or AC-3)frames, or may be otherwise organized (e.g., they may be included in aside mix distinct from an E-AC-3 or AC-3 bitstream). An example ofanother such payload (of or associated with a container included ineither the addbsi field or the Aux field) is a set of loudnessprocessing state metadata associated with the audio content of theframe.

In some such embodiments, the decoder (e.g., decoder 20 of FIG. 6) wouldparse the core header of the container in the Aux field, and extract theinventive object channels and associated metadata from the container(e.g., from the Aux field of the AC-3 or E-AC-3 frame) and/or from thelocation (e.g., side mix) indicated by the core header. After extractingthe payload (object channels and associated metadata), the decoder wouldperform any necessary decoding on the extracted payload.

The core header of each container typically includes: at least one IDvalue indicating the type of payload(s) included in or associated withthe container; substream association indications (indicating whichsubstreams the core header is associated with); and protection bits.Such protection bits (which may consist of or include a hash-basedmessage authentication code or “HMAC”) would typically be useful for atleast one of decryption, authentication, or validation of object relatedmetadata and/or loudness processing state metadata (and optionally alsoother metadata) included in at least one payload included or associatedwith the container, and/or corresponding audio data included in theframe. Substreams may be located “in band” (in the E-AC-3 or AC-3bitstream) or “out of band” (e.g., in a side mix bitstream separate fromthe E-AC-3 or AC-3 bitstream). One type of such payload is a set ofaudio samples of each of one or more of the inventive object channels(related to the bed of speaker channels which is also indicated by theprogram) and the object related metadata associated with each objectchannel. Each object channel is a separate substream, and wouldtypically be identified in the core header. Another type of payload isloudness processing state metadata.

Typically, each payload has its own header (or “payload identifier”).Object level metadata may be carried in each substream which is anobject channel Program level metadata may be included in the core headerof the container and/or in the header for a payload which is a set ofaudio samples of one or more of the inventive object channels (and themetadata associated with each object channel).

In some embodiments, each of the containers in the auxdata (or addbsi)field of the frame has three levels of structure:

a high level structure, including a flag indicating whether the auxdata(or addbsi) field includes metadata (where “metadata” in this contextdenotes the inventive object channels, the inventive object relatedmetadata, and any other audio content or metadata which is carried bythe bitstream but is not conventionally carried in a conventional E-AC-3or AC-3 bitstream which lacks any container of the type beingdescribed), at least one ID value indicating what type(s) of metadataare present, and typically also a value indicating how many bits ofmetadata (e.g., of each type) are present (if metadata is present). Inthis context, an example of one such “type” of metadata is the inventiveobject channel data and associated object related metadata (i.e., a setof audio samples of each of one or more object channels (related to thebed of speaker channels also indicated by the program) and the metadataassociated with each object channel);

an intermediate level structure, comprising a core element for eachidentified type of metadata (e.g., core header, protection values, andpayload ID and payload size values, e.g., of the type mentioned above,for each identified type of metadata); and

a low level structure, comprising each payload for one core element ifat least one such payload is identified by the core element as beingpresent. An example of such a payload is a set of audio samples of eachof one or more object channels (related to the bed of speaker channelswhich is also indicated by the program) and metadata associated witheach object channel Another example of such a payload is a payloadcomprising loudness processing state metadata (“LPSM”), sometimesreferred to as an LPSM payload.

The data values in such a three level structure can be nested. Forexample, the protection value(s) for a payload (e.g., an LPSM payload)identified by a core element can be included after each payloadidentified by the core element (and thus after the core header of thecore element). In one example, a core header could identify a firstpayload (e.g., an LPSM payload) and another payload, payload ID andpayload size values for the first payload could follow the core header,the first payload itself could follow the ID and size values, thepayload ID and payload size value for the second payload could followthe first payload, the second payload itself could follow these ID andsize values, and protection value(s) for either or both of the payloads(or for core element values and either or both of the payloads) couldfollow the last payload.

With reference again to FIG. 6, a user employs controller 23 to selectobjects (indicated by the object based audio program) to be rendered.Controller 23 may be a handheld processing device (e.g., an iPad) whichis programmed to implement a user interface (e.g., an iPad App)compatible with the other elements of the FIG. 6 system. The userinterface may provide (e.g., display on a touch screen) to the user amenu or palette of selectable “preset” mixes of objects and “bed”speaker channel content. The selectable preset mixes may be determinedby object related metadata of the program and typically also by rulesimplemented by subsystem 22 (e.g., rules which subsystem 22 has beenpreconfigured to implement). The user would select from among theselectable mixes by entering commands to controller 23 (e.g., byactuating a touch screen thereof), and in response, controller 23 wouldassert corresponding control data to subsystem 22.

Decoder 20 decodes the speaker channels of the program's bed of speakerchannels, and outputs to subsystem 22 decoded speaker channels. Inresponse to the object based audio program, and in response to controldata from controller 23 indicative of a selected subset of the program'sfull set of object channels to be rendered, decoder 20 decodes (ifnecessary) the selected object channels, and outputs to subsystem 22 theselected (e.g., decoded) object channels (each of which may be a pulsecode modulated or “PCM” bitstream), and object related metadatacorresponding to the selected object channels.

The objects indicated by the decoded object channels typically are orinclude user-selectable audio objects. For example, as indicated in FIG.6, decoder may extract a 5.1 speaker channel bed, an object channel(“Comment-1 mono”) indicative of commentary by an announcer from thehome team's city, an object channel (“Comment-2 mono”) indicative ofcommentary by an announcer from the visiting team's city, an objectchannel (“Fans (home)”) indicative of crowd noise from the home team'sfans who are present at a sporting event, left and right object channels(“Ball Sound stereo”) indicative of sound produced by a game ball as itis struck by sporting event participants, and four object channels(“Effects 4x mono”) indicative of special effects. Any of the “Comment-1mono,” “Comment-2 mono,” “Fans (home),” “Ball Sound stereo,” and“Effects 4x mono” object channels may be selected (after undergoing anynecessary decoding in decoder 20), and each selected one of them wouldbe passed from subsystem 22 to rendering subsystem 24.

As well as the decoded speaker channels, decoded object channels, anddecoded object-related metadata from decoder 20, the inputs to objectprocessing subsystem 22 optionally include external audio objectchannels asserted (e.g., as one or more side mixes of a program whosemain mix is asserted to decoder 20) to the system. Examples of objectsindicated by such external audio object channels include a localcommenter (e.g., monophonic audio content delivered by a radio channel),an incoming Skype call, an incoming twitter connection (converted via atext-to-speech system, not shown in FIG. 6), and system sounds.

Subsystem 22 is configured to output a selected subset of the full setof object channels indicated by the program, and corresponding objectrelated metadata of the program. The object selection may be determinedby user selections (as indicated by control data asserted to subsystem22 from controller 23) and/or rules (e.g., indicative of conditionsand/or constraints) which subsystem 22 has been programmed or otherwiseconfigured to implement. Such rules may be determined by object relatedmetadata of the program and/or by other data (e.g., data indicative ofthe capabilities and organization of the playback system's speakerarray) asserted to subsystem 22 (e.g., from controller 23 or anotherexternal source) and/or by preconfiguring (e.g., programming) subsystem22. In some embodiments, object related metadata provides a set ofselectable “preset” mixes of objects and “bed” speaker channel content.Subsystem 22 typically passes through unchanged (to subsystem 24) thedecoded speaker channels from decoder 20, and processes selected ones ofthe object channels asserted thereto.

The object processing (including object selection) performed bysubsystem 22 is typically controlled by control data from controller 23and object related metadata from decoder 20 (and optionally also objectrelated metadata of side mixes asserted to subsystem 22 other than fromdecoder 20), and typically includes determination of a spatial positionand a level for each selected object (regardless of whether the objectselection is due to user selection or selection by rule application).Typically, default spatial positions and default levels for renderingobject, and optionally also restrictions on user selection of objectsand their spatial positions and levels, are included in object relatedmetadata asserted (e.g., from decoder 20) to subsystem 22. Suchrestrictions may indicate forbidden combinations of objects or forbiddenspatial positions with which selected objects may be rendered (e.g., toprevent selected objects from being rendered too closely to each other).In addition, the loudness of individual selected objects is typicallycontrolled by object processing subsystem 22 in response to control dataentered using controller 23, and/or default levels indicated by objectrelated metadata (e.g., from decoder 20), and/or by preconfiguration ofsubsystem 22.

Typically, the decoding performed by decoder 20 includes extraction(from the input program) of metadata indicating the type of audiocontent of each object indicated by the program (e.g., the type ofsporting event indicated by the program's audio content, and names orother identifying indicia (e.g., team logos) of selectable and defaultobjects indicated by the program). Controller 23 and object processingsubsystem 22 receive this metadata or relevant information indicated bythe metadata. Typically also, controller 23 receives (e.g., isprogrammed with) information regarding the playback capability of theuser's audio system (e.g., the number of speakers, and an assumedplacement or other assumed organization of the speakers).

Spatial rendering subsystem 24 of FIG. 6 (or subsystem 24 with at leastone downstream device or system) is configured to render the audiocontent output from subsystem 22 for playback by speakers of the user'splayback system. One or more of optionally included digital audioprocessing subsystems 25, 26, and 27 may implement post-processing onthe output of subsystem 24.

Spatial rendering subsystem 24 is configured to map, to the availablespeaker channels, the audio object channels selected by objectprocessing subsystem 22 (e.g., default-selected objects, and/oruser-selected objects which have been selected as a result of userinteraction using controller 23), using rendering parameters output fromsubsystem 22 (e.g., user-selected and/or default values of spatialposition and level) which are associated with each selected object.Spatial rendering system 24 also receives the decoded bed of speakerchannels passed through by subsystem 22. Typically, subsystem 24 is anintelligent mixer, and is configured to determine speaker feeds for theavailable speakers including by mapping one, two, or more than twoselected object channels to each of a number of individual speakerchannels, and mixing the selected object channel(s) with “bed” audiocontent indicated by each corresponding speaker channel of the program'sspeaker channel bed.

The number of output speaker channels may vary between 2.0 and 7.1, andthe speakers to be driven to render the selected audio object channels(in a mix with the “bed” audio content) may be assumed to be located ina (nominally) horizontal plane in the playback environment. In suchcases, the rendering is performed so that the speakers can be driven toemit sound that will be perceived as emitting from distinct objectlocations in the plane of the speakers (i.e., one object location, orone sequence of object locations along a trajectory, for each selectedor default object), mixed with sound determined by the “bed” audiocontent.

In some embodiments, the number of full range speakers to be driven torender the audio can be any number in a wide range (it is notnecessarily limited to be in the range from 2 to 7), and thus the numberof output speaker channels is not limited to be in the range from 2.0and 7.1.

In some embodiments, the speakers to be driven to render the audio areassumed to be located in arbitrary locations in the playbackenvironment; not merely in a (nominally) horizontal plane. In some suchcases, metadata included in the program indicates rendering parametersfor rendering at least one object of the program at any apparent spatiallocation (in a three dimensional volume) using a three-dimensional arrayof speakers. For example, an object channel may have correspondingmetadata indicating a three-dimensional trajectory of apparent spatialpositions at which the object (indicated by the object channel) is to berendered. The trajectory may include a sequence of “floor” locations (inthe plane of a subset of speakers which are assumed to be located on thefloor, or in another horizontal plane, of the playback environment), anda sequence of “above-floor” locations (each determined by driving asubset of the speakers which are assumed to be located in at least oneother horizontal plane of the playback environment). In such cases, therendering can be performed in accordance with the present invention sothat the speakers can be driven to emit sound (determined by therelevant object channel) that will be perceived as emitting from asequence of object locations in the three-dimensional space whichincludes the trajectory, mixed with sound determined by the “bed” audiocontent. Subsystem 24 may be configured to implement such rendering, orsteps thereof, with remaining steps of the rendering being performed bya downstream system or device (e.g., rendering subsystem 35 of FIG. 6).

Optionally, a digital audio processing (DAP) stage (e.g., one for eachof a number of predetermined output speaker channel configurations) iscoupled to the output of spatial rendering subsystem 24 to performpost-processing on the output of the spatial rendering subsystem.Examples of such processing include intelligent equalization or (in caseof a stereo output) speaker virtualization processing.

The output of the FIG. 6 system (e.g., the output of the spatialrendering subsystem, or a DAP stage following the spatial renderingstage) may be PCM bitstreams (which determine speaker feeds for theavailable speakers). For example, in the case that the user's playbacksystem includes a 7.1 array of speakers, the system may output PCMbitstreams (generated in subsystem 24) which determine speaker feeds forthe speakers of such array, or a post-processed version (generated inDAP 25) of such bitstreams. For another example, in the case that theuser's playback system includes a 5.1 array of speakers, the system mayoutput PCM bitstreams (generated in subsystem 24) which determinespeaker feeds for the speakers of such array, or a post-processedversion (generated in DAP 26) of such bitstreams. For another example,in the case that the user's playback system includes only left and rightspeakers, the system may output PCM bitstreams (generated in subsystem24) which determine speaker feeds for the left and right speakers, or apost-processed version (generated in DAP 27) of such bitstreams.

The FIG. 6 system optionally also includes one or both of re-encodingsubsystems 31 and 33. Re-encoding subsystem 31 is configured tore-encode the PCM bitstream (indicative of feeds for a 7.1 speakerarray) output from DAP 25 as an E-AC-3 encoded bitstream, and theresulting encoded (compressed) E-AC-3 bitstream may be output from thesystem. Re-encoding subsystem 33 is configured to re-encode the PCMbitstream (indicative of feeds for a 5.1 speaker array) output from DAP27 as an AC-3 or E-AC-3 encoded bitstream, and the resulting encoded(compressed) AC-3 or E-AC-3 bitstream may be output from the system.

The FIG. 6 system optionally also includes re-encoding (or formatting)subsystem 29 and downstream rendering subsystem 35 coupled to receivethe output of subsystem 29. Subsystem 29 is coupled to receive data(output from subsystem 22) indicative of the selected audio objects (ordefault mix of audio objects), corresponding object related metadata,and the bed of speaker channels, and is configured to re-encode (and/orformat) such data for rendering by subsystem 35. Subsystem 35, which maybe implemented in an AVR or soundbar (or other system or devicedownstream from subsystem 29), is configured to generate speaker feeds(or bitstreams which determine speaker feeds) for the available playbackspeakers (speaker array 36), in response to the output of subsystem 29.For example, subsystem 29 may be configured to generate encoded audio,by re-encoding the data indicative of the selected (or default) audioobjects, corresponding metadata, and bed of speaker channels, into asuitable format for rendering in subsystem 35, and to transmit theencoded audio (e.g., via an HDMI link) to subsystem 35. In response tospeaker feeds generated by (or determined by the output of) subsystem35, the available speakers 36 would emit sound indicative of a mix ofthe speaker channel bed and the selected (or default) object(s), withthe object(s) having apparent source location(s) determined by objectrelated metadata of subsystem 29′s output. When subsystems 29 and 35 areincluded, rendering subsystem 24 is optionally omitted from the system.

In some embodiments, the invention is a distributed system for renderingobject based audio, in which a portion (i.e., at least one step) of therendering (e.g., selection of audio objects to be rendered and selectionof characteristics of the rendering of each selected object, asperformed by subsystem 22 and controller 23 of the FIG. 6 system) isimplemented in a first subsystem (e.g., elements 20, 22, and 23 of FIG.6, implemented in a set top device, or a set top device and a handheldcontroller) and another portion of the rendering (e.g., immersiverendering in which speaker feeds, or signals which determine speakerfeeds, are generated in response to the output of the first subsystem)is implemented in a second subsystem (e.g., subsystem 35, implemented inan AVR or soundbar). Some embodiments which provide distributedrendering also implement latency management to account for the differenttimes at which and different subsystems in which portions of the audiorendering (and any processing of video which corresponds to the audiobeing rendered) are performed.

In some embodiments of the inventive playback system, each decoder andobject processing subsystem (sometimes referred to as a personalizationengine) are implemented in a set top device (STB). For example, elements20 and 22 of FIG. 6, and/or all elements of the FIG. 7 system may beimplemented in an STB. In some embodiments of the inventive playbacksystem, multiple renderings are performed on the output of thepersonalization engine to ensure that all STB outputs (e.g., HDMI,S/PDIF, and stereo analog outputs of the STB) are enabled. Optionally,selected object channels (and corresponding object related metadata) arepassed on (with the decoded bed of speaker channels) from the STB to adownstream device (e.g., an AVR or soundbar) configured to render a mixof the object channels and the bed of speaker channels.

In a class of embodiments, the inventive object based audio programincludes a set of bitstreams (multiple bitstreams, which may be referredto as “substreams”) which are generated and transmitted in parallel. Insome embodiments in this class, multiple decoders are employed to decodecontent of the substreams (e.g., the program includes multiple E-AC-3substreams and the playback system employs multiple E-AC-3 decoders todecode content of the substreams). FIG. 7 is a block diagram of aplayback system configured to decode and render an embodiment of theinventive object based audio program which comprises multiple serialbitstreams which are delivered in parallel.

The playback system of FIG. 7 is a variation on the FIG. 6 system inwhich the object based audio program includes multiple bitstreams (B1,B2, BN, where N is some positive integer) which are delivered to theplayback system in parallel and received by the playback system. Each ofbitstreams (“substreams”) B1, B2, . . . , and BN is a serial bitstreamwhich includes time codes or other synchronization words (referred to as“sync words” for convenience with reference to FIG. 7) to allow thesubstreams to be synchronized or time aligned with each other. Eachsubstream also includes a different subset of a full set of objectchannels and corresponding object related metadata, and at least one ofthe substreams includes a bed of speaker channels. For example, in eachof substreams B1, B2, . . . , BN, each container which includes objectchannel content and object related metadata includes a unique ID or timestamp.

The FIG. 7 system includes N deformatters 50, 51, . . . , 53, eachcoupled and configured to parse a different one of the input substreams,and to assert the metadata (including the synch words thereof) and audiocontent thereof to bitstream synchronization stage 59.

Deformatter 50 is configured to parse substream B1, and to assert thesync words (T1) thereof, other metadata and object channel content (M1)thereof (including object related metadata and at least one objectchannel of the program), and speaker channel audio content (A1) thereof(including at least one speaker channel of the program's bed) tobitstream synchronization stage 59. Similarly, deformatter 51 isconfigured to parse substream B2, and to assert the sync words (T2)thereof, other metadata and object channel content (M2) thereof(including object related metadata and at least one object channel ofthe program), and speaker channel audio content (A2) thereof (includingat least one speaker channel of the program's bed) to bitstreamsynchronization stage 59. Similarly, deformatter 53 is configured toparse substream BN, and to assert the sync words (TN) thereof, othermetadata and object channel content (MN) thereof (including objectrelated metadata and at least one object channel of the program), andspeaker channel audio content (AN) thereof (including at least onespeaker channel of the program's bed) to bitstream synchronization stage59.

Bitstream synchronization stage 59 of the FIG. 7 system typicallyincludes buffers for the audio content and metadata of the substreamsB1, B2, . . . , BN, and a stream offset compensation element which iscoupled and configured to use the sync words of each of the substreamsto determine any misalignment of data in the input substreams (e.g.,which may occur due to the likelihood that tight synchronism among themis lost in distribution/contribution since each bitstream is typicallycarried over an independent interface and/or track within a media file).The stream offset compensation element of stage 59 is typically alsoconfigured to correct any determined misalignment by assertingappropriate control values to the buffers containing the audio data andmetadata of the bitstreams, to cause time-aligned bits of the speakerchannel audio data to be read from the buffers to decoders (includingdecoders 60, 61, and 63), each of which is coupled to a correspondingone of the buffers, and to cause time-aligned bits of the object channelaudio data and metadata to be read from the buffers to object datacombining stage 66.

Time-aligned bits of speaker channel audio content A1′ from substream B1are read from stage 59 to decoder 60, and time-aligned bits of objectchannel content and metadata M1′ from substream B1 are read from stage59 to metadata combiner 66. Decoder 60 is configured to perform decodingon the speaker channel audio data asserted thereto, and to assert theresulting decoded speaker channel audio to object processing andrendering subsystem 67.

Similarly, time-aligned bits of speaker channel audio content A2′ fromsubstream B2 are read from stage 59 to decoder 61, and time-aligned bitsof object channel content and metadata M2′ from substream B2 are readfrom stage 59 to metadata combiner 66. Decoder 61 is configured toperform decoding on the speaker channel audio data asserted thereto, andto assert the resulting decoded speaker channel audio to objectprocessing and rendering subsystem 67.

Similarly, time-aligned bits of speaker channel audio content AN′ fromsubstream BN are read from stage 59 to decoder 63, and time-aligned bitsof object channel content and metadata MN′ from substream BN are readfrom stage 59 to metadata combiner 66. Decoder 63 is configured toperform decoding on the speaker channel audio data asserted thereto, andto assert the resulting decoded speaker channel audio to objectprocessing and rendering subsystem 67.

For example, each of substreams B 1, B2, . . . , BN may be an E-AC-3substream, and each of decoders 60, 61, 63, and any other decoder(s)coupled to subsystem 59 in parallel with decoders 60, 61, and 63, may bean E-AC-3 decoder configured to decode speaker channel content of one ofthe input E-AC-3 substreams.

Object data combiner 66 is configured to assert the time-aligned objectchannel data and metadata for all the object channels of the program inan appropriate format to object processing and rendering subsystem 67.

Subsystem 67 is coupled to the output of combiner 66 and to the outputsof decoders 60, 61, and 63 (and any other decoder(s) coupled in parallelwith decoders 60, 61, and 63 between subsystems 59 and 67), andcontroller 68 is coupled to subsystem 67. Subsystem 67 includes asubsystem configured to perform object processing on the outputs ofcombiner 66 and the decoders (e.g., including the steps performed bysubsystem 22 of the FIG. 6 system, or variations on such steps) in aninteractive manner in accordance with an embodiment of the invention, inresponse to control data from controller 68. Controller 68 may beconfigured to perform the operations which controller 23 of the FIG. 6system is configured to perform (or variations on such operations) inresponse to input from a user. Subsystem 67 also includes a subsystemconfigured to perform rendering on speaker channel audio and objectchannel audio data asserted thereto (e.g., the operations performed byrendering subsystem 24, or subsystems 24, 25, 26, 31, and 33 of the FIG.6 system, or subsystems 24, 25, 26, 31, 33, 29, and 35 of the FIG. 6system, or variations on such operations) in accordance with anembodiment of the invention.

In one implementation of the FIG. 7 system, each of substreams B1, B2, .. . , BN is a Dolby E bitstream. Each such Dolby E bitstream comprises asequence of bursts. Each burst may carry speaker channel audio content(a “bed of speaker channels) and a subset of a full object channel set(which may be a large set) of the inventive object channels and objectrelated metadata (i.e., each burst may indicate some object channels ofthe full object channel set and corresponding object related metadata).Each burst of a Dolby E bitstream typically occupies a time periodequivalent to that of a corresponding video frame. Each Dolby Ebitstream in the set includes synchronization words (e.g., time codes)to allow the bitstreams in the set to be synchronized or time alignedwith each other. For example, in each bitstream, each containerincluding object channel content and object related metadata couldinclude a unique ID or time stamp to allow the bitstreams in the set tobe synchronized or time aligned with each other. In the notedimplementation of the FIG. 7 system, each of deformatters 50, 51, and 53(and any other deformatter(s) coupled in parallel with deformatters 50,51, and 53) is an SMPTE 337 deformatter, and each of decoders 60, 61,63, and any other decoder(s) coupled to subsystem 59 in parallel withdecoders 60, 61, and 63, may be a Dolby E decoder.

In some embodiments of the invention, object related metadata of anobject based audio program includes durable metadata. For example, theobject related metadata included in the program input to subsystem 20 ofthe FIG. 6 system may include non-durable metadata (e.g., a defaultlevel and/or rendering position or trajectory, for a user-selectableobject) which can be changed at at least one point in the broadcastchain (from the content creation facility which generated the program tothe user interface implemented by controller 23) and durable metadatawhich is not intended to be changeable (or cannot be changed) afterinitial generation of the program (typically, in a content creationfacility). Examples of durable metadata include: an object ID for eachuser-selectable object or other object or set of objects of the program;and time codes or other synchronization words indicative of timing ofeach user-selectable object, or other object, relative to audio contentof the bed of speaker channels or other elements of the program. Durablemetadata is typically preserved throughout the entire broadcast chainfrom content creation facility to user interface, throughout the entireduration of a broadcast of the program or even also during re-broadcastsof the program. In some embodiments, the audio content (and associatedmetadata) of at least one user-selectable object is sent in a main mixof the object based audio program, and at least some durable metadata(e.g., time codes) and optionally also audio content (and associatedmetadata) of at least one other object is sent in a side mix of theprogram.

Durable, object related metadata in some embodiments of the inventiveobject based audio program is employed to preserve (e.g., even afterbroadcast of the program) a user selected mix of object content and bed(speaker channel) content. For example, this may provide the selectedmix as a default mix each time the user a program of a specific type(e.g., any soccer game) or each time the user watches any program (ofany type), until the user changes his/her selection. For example, duringbroadcast of a first program, the user may employ controller 23 (of theFIG. 6 system) to select a mix including an object having a durable ID(e.g., an object identified by controller 23′s user interface as a “hometeam crowd noise” object, where the durable ID indicates “home teamcrowd noise”). Then, each time the user watches (and listens to) anotherprogram (which includes an object having the same durable ID), theplayback system will automatically render the program with the same mix(i.e., the program's bed of speaker channels mixed with the program's“home team crowd noise” object channel), until the user changes the mixselection. Durable, object related metadata in some embodiments of theinventive object based audio program may cause rendering of some objectsto be mandatory (e.g., despite a user desire to defeat such rendering)during an entire program.

In some embodiments, object related metadata provides a default mix ofobject content and bed (speaker channel) content, with default renderingparameters (e.g., default spatial locations of rendered objects). Forexample, the object related metadata of the program input to subsystem20 of the FIG. 6 system may be default mix of object content and bed(speaker channel) content, with default rendering parameters, andsubsystems 22 and 24 will cause the program to be rendered with defaultmix, and with the default rendering parameters, unless a user employscontroller 23 to select another mix of object content and bed contentand/or another set of rendering parameters.

In some embodiments, object related metadata provides a set ofselectable “preset” mixes of objects and “bed” speaker channel content,each preset mix having a predetermined set of rendering parameters(e.g., spatial locations of rendered objects). These may be presented bya user interface of the playback system as a limited menu or palette ofavailable mixes (e.g., a limited menu or palette displayed by controller23 of the FIG. 6 system). Each preset mix (and/or each selectableobject) may have a durable ID (e.g., name, label or logo). Controller 23(or the controller of another embodiment of the inventive playbacksystem) may be configured to display an indication of such ID (e.g., onthe touch screen of an iPad implementation of controller 23). Forexample, there may be a selectable “home team” mix with an ID (e.g., ateam logo) that is durable, regardless of changes (e.g., made by thebroadcaster) to details of the audio content or nondurable metadata ofeach object of the preset mix.

In some embodiments, object related metadata of a program (or apreconfiguration of the playback or rendering system, not indicated bymetadata delivered with the program) provides constraints or conditionson selectable mixes of objects and bed (speaker channel) content. Forexample, an implementation of the FIG. 6 system may implement digitalrights management (DRM), and more specifically may implement a DRMhierarchy to allow a user of the FIG. 6 system to have “tiered” accessto a set of audio objects included in an object based audio program. Ifthe user (e.g., a customer associated with the playback system) paysmore money (e.g., to the broadcaster), the user may be authorized todecode and select (and hear) more audio objects of the program.

For another example, object related metadata may provide constraints onuser selection of objects. An example of such a constraint is that if auser employs controller 23 to select for rendering both a “home teamcrowd noise” object and a “home team announcer” object of a program(i.e., for inclusion in the mix determined by subsystem 24 of FIG. 6),metadata included in the program may ensure that subsystem 24 causes thetwo selected objects to be rendered with predetermined relative spatiallocations. The constraints may be determined (at least in part) by data(e.g., user-entered data) regarding the playback system. For example, ifthe playback system is a stereo system (including only two speakers),object processing subsystem 24 (and/or controller 23) of the FIG. 6system may be configured to prevent user selection of mixes (identifiedby object related metadata) that cannot be rendered with adequatespatial resolution by only two speakers. For another example, objectprocessing subsystem 24 (and/or controller 23) of the FIG. 6 system mayremove some delivered objects from the category of selectable objectsfor legal (e.g., DRM) reasons or other reasons (e.g. based on bandwidthof the delivery channel) indicated by object related metadata (and/orother data entered to the playback system). The user may pay the contentcreator or broadcaster for more bandwidth, and as a result the system(e.g., object processing subsystem 24 and/or controller 23 of the FIG. 6system) may allow the user to select from a larger menu of selectableobjects and/or object/bed mixes.

Some embodiments of the invention (e.g., implementations of the playbacksystem of FIG. 6 which include above-described elements 29 and 35)implement distributed rendering. For example, default or selected objectchannels (and corresponding object related metadata) of a program arepassed on (with a decoded bed of speaker channels) from a set top device(e.g., from subsystems 22 and 29 of an implementation of the FIG. 6system) to a downstream device (e.g., subsystem 35 of FIG. 6,implemented in an AVR or soundbar downstream from the set top device(STB) in which subsystems 22 and 29 are implemented). The downstreamdevice is configured to render a mix of the object channels and the bedof speaker channels. The STB may partially render the audio and thedownstream device may complete the rendering (e.g., by generatingspeaker feeds for driving a specific top tier of speakers (e.g., ceilingspeakers) to place an audio object in a specific apparent sourceposition, where the STB's output merely indicates that the object can berendered in some unspecified way in some unspecified top tier ofspeakers). For example, the STB may not have knowledge of the specificorganization of the speakers of the playback system, but the downstreamdevice (e.g., AVR or soundbar) may have such knowledge.

In some embodiments, the object based audio program (e.g., the programinput to subsystem 20 of the FIG. 6 system, or to elements 50, 51, and53 of the FIG. 7 system) is or includes at least one AC-3 (or E-AC-3)bitstream, and each container of the program which includes objectchannel content (and/or object related metadata) is included in anauxdata field (e.g., the AUX segment shown in FIG. 1 or FIG. 4) at theend of a frame of the bitstream. In some such embodiments, each frame ofthe AC-3 or E-AC-3 bitstream includes one or two metadata containers.One container can be included in the Aux field of the frame, and anothercontainer can be included in the addbsi field of the frame. Eachcontainer has a core header and includes (or is associated with) one ormore payloads. One such payload (of or associated with a containerincluded in the Aux field) may be a set of audio samples of each of oneor more of the inventive object channels (related to the bed of speakerchannels which is also indicated by the program) and the object relatedmetadata associated with each object channel. The core header of eachcontainer typically includes at least one ID value indicating the typeof payload(s) included in or associated with the container; substreamassociation indications (indicating which substreams the core header isassociated with); and protection bits. Typically, each payload has itsown header (or “payload identifier”). Object level metadata may becarried in each substream which is an object channel.

In other embodiments, the object based audio program (e.g., the programinput to subsystem 20 of the FIG. 6 system, or to elements 50, 51, and53 of the FIG. 7 system) is or includes a bitstream which is not an AC-3bitstream or an E-AC-3 bitstream. In some embodiments, the object basedaudio program is or includes at least one Dolby E bitstream, and theobject channel content and object related metadata of the program (e.g.,each container of the program which includes object channel contentand/or object related metadata) is included in bit locations of theDolby E bitstream that conventionally do not conventionally carry usefulinformation. Each burst of a Dolby E bitstream occupies a time periodequivalent to that of a corresponding video frame. The object channels(and object related metadata) may be included in the guard bands betweenDolby E bursts and/or in the unused bit locations within each of datastructures (each having the format of an AES3 frame) within each Dolby Eburst. For example, each guard band consists of a sequence of segments(e.g., 100 segments), each of the first X segments (e.g., X=20) of eachguard band includes the object channels and object related metadata, andeach of the remaining segments of said each guard band may include aguard band symbol. In some embodiments, the object channels and objectrelated metadata of Dolby E bitstreams are included in metadatacontainers. Each container has a core header and includes (or isassociated with) one or more payloads. One such payload (of orassociated with a container included in the Aux field) may be a set ofaudio samples of each of one or more of the inventive object channels(related to the bed of speaker channels which is also indicated by theprogram) and the object related metadata associated with each objectchannel The core header of each container typically includes at leastone ID value indicating the type of payload(s) included in or associatedwith the container; substream association indications (indicating whichsubstreams the core header is associated with); and protection bits.Typically, each payload has its own header (or “payload identifier”).Object level metadata may be carried in each substream which is anobject channel.

In some embodiments, the object based audio program (e.g., the programinput to subsystem 20 of the FIG. 6 system, or to elements 50, 51, and53 of the FIG. 7 system) is decodable, and the speaker channel contentthereof is renderable, by a legacy decoder and legacy rendering system(which is not configured to parse the inventive object channels andobject related metadata). The same program may be rendered in accordancewith some embodiments of the invention by set top device (or otherdecoding and rendering system) which is configured (in accordance withan embodiment of the invention) to parse the inventive object channelsand object related metadata and render a mix of speaker channel andobject channel content indicated by the program.

Some embodiments of the invention are intended to provide a personalized(and preferably immersive) audio experience for end consumers inresponse to a broadcast program, and/or to provide new methods for usingmetadata in a broadcast pipeline. Some embodiments improve microphonecapture (e.g., stadium microphone capture) to generate audio programswhich provide a more immersive experience for the end consumer, modifyexisting production, contribution and distribution workflows to allowobject channel(s) and metadata of the inventive object based audioprogram(s) to flow through the professional chain, and create a newplayback pipeline (e.g., one implemented in a set top device) thatsupports the inventive object channel(s) and metadata as well asconventionally broadcast audio (e.g., the bed of speaker channelsincluded in some embodiments of the inventive broadcast audio program).

FIG. 8 is a block diagram of a broadcast system configured to generatean object based audio program (and a corresponding video program) inaccordance with an embodiment of the invention, for broadcast. A set ofX microphones (where X is an integer), including microphones 100, 101,102, and 103, of the FIG. 8 system are positioned to capture audiocontent to be included in the program, and their outputs are coupled toinputs of audio console 104.

In a class of embodiments, the program includes interactive audiocontent which is indicative of the atmosphere in or at, and/orcommentary on a spectator event (e.g., a soccer or rugby game, a car ormotorcycle race, or another sporting event). In some embodiments, theaudio content of the program is indicative of multiple audio objects(including user-selectable objects or object sets, and typically also adefault set of objects to be rendered in the absence of object selectionby the user) and a mix (or “bed”) of speaker channels of the program.The bed of speaker channels may be a conventional mix (e.g., a 5.1channel mix) of speaker channels of a type that might be included in aconventional broadcast program which does not include an object channel.

A subset of the microphones (e.g., microphones 100 and 101 andoptionally also other microphones whose outputs are coupled to audioconsole 104) is a conventional array of microphones which, in operation,captures audio (to be encoded and delivered as a bed of speakerchannels). In operation, another subset of the microphones (e.g.,microphones 102 and 103 and optionally also other microphones whoseoutputs are coupled to audio console 104) captures audio (e.g., crowdnoise and/or other “objects”) to be encoded and delivered as objectchannels of the program. For example, the microphone array of the FIG. 8system may include: at least one microphone (e.g., microphone 100)implemented as a soundfield microphone and permanently installed in astadium (e.g., a soundfield microphone having a heater installed withit); at least one stereo microphone (e.g., microphone 102, implementedas a Sennheiser MKH416 microphone or another stereo microphone) pointedat the location of spectators who support one team (e.g., the hometeam), and at least one other stereo microphone (e.g., microphone 103,implemented as a Sennheiser MKH416 microphone or another stereomicrophone) pointed at the location of spectators who support the otherteam (e.g., the visiting team).

The inventive broadcasting system may include a mobile unit (which maybe a truck, and is sometimes referred to as a “match truck”) locatedoutside of a stadium (or other event location), which is the firstrecipient of audio feeds from microphones in the stadium (or other eventlocation). The match truck generates the object based audio program (tobe broadcast) including by encoding audio content from microphones fordelivery as object channels of the program, generating correspondingobject related metadata (e.g., metadata indicative of spatial locationat which each object should be rendered) and including such metadata inthe program, and encoding audio content from some microphones fordelivery as a bed of speaker channels of the program.

For example, in the FIG. 8 system, console 104, object processingsubsystem 106 (coupled to the outputs of console 104), embeddingsubsystem 108, and contribution encoder 110 may be installed in a matchtruck. The object based audio program generated in subsystem 106 may becombined (e.g., in subsystem 108) with video content (e.g., from cameraspositioned in the stadium) to generate a combined audio and video signalwhich is then encoded (e.g., by encoder 110), thereby generating anencoded audio/video signal for broadcast (e.g., by delivery subsystem 5of FIG. 5). It should be understood that a playback system which decodesand renders such an encoded audio/video signal would include a subsystem(not specifically shown in the drawings) for parsing the audio contentand the video content of the delivered audio/video signal, and asubsystem (e.g., one similar or identical to the FIG. 6 system) fordecoding and rendering the audio content in accordance with anembodiment of the invention, and another subsystem (not specificallyshown in the drawings) for decoding and rendering the video content.

The audio output of console 104 may include a 5.1 speaker channel bed(labeled “5.1 neutral” in FIG. 8) indicative of sound captured at asporting event, audio content of a stereo object channel (labeled “2.0home”) indicative of crowd noise from the home team's fans who arepresent at the event, audio content of a stereo object channel (labeled“2.0 away”) indicative of crowd noise from the visiting team's fans whoare present at the event, object channel audio content (labeled “1.0comm1”) indicative of commentary by an announcer from the home team'scity, object channel audio content (labeled “1.0 comm2”) indicative ofcommentary by an announcer from the visiting team's city, and objectchannel audio content (labeled “1.0 ball kick”) indicative of soundproduced by a game ball as it is struck by sporting event participants.

Object processing subsystem 106 is configured to organize (e.g., group)audio streams from console 104 into object channels (e.g., to group theleft and right audio streams labeled “2.0 away” into a visiting crowdnoise object channel) and/or sets of object channels, to generate objectrelated metadata indicative of the object channels (and/or objectchannel sets), and to encode the object channels (and/or object channelsets), object related metadata, and the speaker channel bed (determinedfrom audio streams from console 104) as an object based audio program(e.g., an object based audio program encoded as a Dolby E bitstream).Typically also, subsystem 106 is configured to render (and play on a setof studio monitor speakers) at least a selected subset of the objectchannels (and/or object channel sets) and the speaker channel bed(including by using the object related metadata to generate a mixindicative of the selected object channel(s) and speaker channels) sothat the played back sound can be monitored by the operator(s) ofconsole 104 and subsystem 106 (as indicated by the “monitor path” ofFIG. 8).

The interface between subsystem 104′s outputs and subsystem 106′s inputsmay be a multichannel audio digital interface (“MADI”).

In operation, subsystem 108 of the FIG. 8 system combines the objectbased audio program generated in subsystem 106 with video content (e.g.,from cameras positioned in a stadium) to generate a combined audio andvideo signal which is asserted to encoder 110. The interface betweensubsystem 108′s output and subsystem 110′s input may be a highdefinition serial digital interface (“HD-SDI”). In operation, encoder110 encodes the output of subsystem 108, thereby generating an encodedaudio/video signal for broadcast (e.g., by delivery subsystem 5 of FIG.5).

In some embodiments, a broadcast facility is (e.g., subsystems 106, 108,and 110 of the FIG. 8 system are) configured to generate multiple objectbased audio programs (e.g., object based audio programs indicated bymultiple encoded audio/video signals output from subsystem 110 of FIG.8) indicative of captured sound. Examples of such object based audioprograms include a 5.1 flattened mix, an international mix, and adomestic mix. For example, all the programs may include a common bed ofspeaker channels, but the object channels of the programs (and/or themenu of selectable object channels determined by the programs, and/orselectable or nonselectable rendering parameters for rendering andmixing the object channels) may differ from program to program.

In some embodiments, a facility of a broadcaster or other contentcreator (e.g., subsystems 106, 108, and 110 of the FIG. 8 system) isconfigured to generate a single object based audio program (i.e., amaster) which can be rendered in any of a variety of different playbackenvironments (e.g., 5.1 channel domestic playback systems, 5.1 channelinternational playback systems, and stereo playback systems). The masterdoes not need to be mixed (e.g., downmixed) for broadcast to consumersin any specific environment.

As noted above, in some embodiments of the invention, object relatedmetadata of a program (or a preconfiguration of the playback orrendering system, not indicated by metadata delivered with the program)provides constraints or conditions on selectable mixes of objects andbed (speaker channel) content. For example, an implementation of theFIG. 6 system may implement a DRM hierarchy to allow a user to havetiered access to a set of object channels included in an object basedaudio program. If the user pays more money (e.g., to the broadcaster),the user may be authorized to decode, select, and render more objectchannels of the program.

Examples of constraints and conditions on user selection of objects (orgroups of objects) will be described with reference to FIG. 9. In FIG.9, program “P0” includes seven object channels: object channel “N0”indicative of neutral crowd noise, object channel “N1” indicative ofhome crowd noise, object channel “N2” indicative of away crowd noise,object channel “N3” indicative of official commentary (e.g. broadcastcommentary by a commercial radio announcer) on an event, object channel“N4” indicative of fan commentary on the event, object channel “N5”indicative of public address announcements at the event, and objectchannel “N6” indicative of an incoming twitter connection (converted viaa text-to-speech system) pertaining to the event.

Default indicating metadata included in program P0 indicates a defaultobject set (one or more “default” objects) and default renderingparameter set (e.g., the spatial position of each default object in thedefault object set) to be included (by default) in the rendered mix of“bed” speaker channel content and object channel content indicated bythe program. For example, the default object set may be a mix of objectchannel “N0” (indicative of neutral crowd noise) rendered in a diffusemanner (e.g., so as not to be perceived as emitting from any specificsource location) and object channel “N3” (indicative of officialcommentary) rendered so as to be perceived as emitting from a sourcelocation directly in front of the listener (i.e., at an azimuth of 0degrees with respect to the listener).

Program P0 (of FIG. 9) also includes metadata indicating multiple setsof user selectable preset mixes, each preset mix determined by a subsetof the object channels of the program and a corresponding renderingparameter set. The user selectable preset mixes may be presented as amenu on a user interface of a controller of the playback system (e.g., amenu displayed by controller 23 of the FIG. 6 system). For example, onesuch preset mix is a mix of object channel “N0” of FIG. 9 (indicative ofneutral crowd noise) and object channel “N1” (indicative of home crowdnoise) and object channel “N4” (indicative of fan commentary), renderedso that the channel N0 and N1 content in the mix is perceived asemitting from a source location directly behind the listener (i.e., atan azimuth of 180 degrees with respect to the listener), with the levelof channel N1 content in the mix being 3 dB less than the level ofchannel N0 in the mix, and with the channel N4 content in the mixrendered in a diffuse manner (e.g., so as not to be perceived asemitting from any specific source location).

The playback system may implement a rule (e.g., a grouping rule “G”indicated in FIG. 9, determined by metadata of the program) that eachuser selectable preset mix that includes at least one of object channelsN0, N1, and N2 must include content of object channel N0 alone, orcontent of object channel N0 mixed with content of at least one ofobject channels N1 and N2. The playback system may also implement a rule(e.g., a condition rule “C1” indicated in FIG. 9, determined by metadataof the program) that each user selectable preset mix that includescontent of object channel N0 mixed with content of at least one ofobject channels N1 and N2 must include content of object channel N0mixed with content of object channel N1, or it must include content ofobject channel N0 mixed with content of object channel N2.

The playback system may also implement a rule (e.g., a condition rule“C2” indicated in FIG. 9, determined by metadata of the program) thateach user selectable preset mix that includes content of at least one ofobject channels N3 and N4 must include either content of object channelN3 alone, or it must include content of object channel N4 alone.

Some embodiments of the invention implement conditional decoding (and/orrendering) of object channels of an object based audio program. Forexample, the playback system may be configured to allow object channelsto be conditionally decoded based on the playback environment or theuser's rights. For example, if a DRM hierarchy is implemented to allowcustomers to have “tiered” access to a set of audio object channelsincluded in an object based audio program, the playback system may beautomatically configured (by control bits included in metadata of theprogram) to prevent decoding and selection for rendering of some of theobjects unless the playback system is notified that the user hassatisfied at least one condition (e.g., paying a specific amount ofmoney to the content provider). For example, the user may need topurchase a right in order to listen to “official commentary” objectchannel N3 of program P0 of FIG. 9, and the playback system mayimplement condition rule “C2” indicated in FIG. 9 such that objectchannel N3 cannot be selected unless the playback system is notifiedthat the user of the playback system has purchased the necessary right.

For another example, the playback system may be automatically configured(by control bits included in metadata of the program, indicating aspecific format of the available playback speaker array) to preventdecoding and selection of some of the objects if the playback speakerarray does not meet a condition (e.g., the playback system may implementcondition rule “C1” indicated in FIG. 9 such that a preset mix of objectchannels N0 and N1 cannot be selected unless the playback system isnotified that a 5.1 speaker array is available for rendering theselected content, but not if the only available speaker array is a 2.0speaker array).

In some embodiments, the invention implements rule based object channelselection, in which at least one predetermined rule determines whichobject channel(s) of an object based audio program are rendered (e.g.,with a bed of speaker channels). The user may also specify at least onerule for object channel selection (e.g., by selecting from a menu ofavailable rules presented by a user interface of a playback systemcontroller), and the playback system (e.g., object processing subsystem22 of the FIG. 6 system) may be configured to apply each such rule todetermine which object channel(s) of an object based audio program to berendered should be included in the mix to be rendered (e.g., bysubsystem 24, or subsystems 24 and 35, of the FIG. 6 system). Theplayback system may determine from object related metadata in theprogram which object channel(s) of the program satisfy the predeterminedrule(s).

For a simple example, consider the case that the object based audioprogram is indicative of a sporting event. Instead of manipulating acontroller (e.g., controller 23 of FIG. 6) to perform static select of aspecific set of objects included in the program (e.g., radio commentaryfrom a specific team, or car, or bike), the user manipulates thecontroller to set up a rule (e.g., to automatically select, forrendering, object channels indicative of whatever team, or car, or bikeis winning or in first place). The rule is applied by the playbacksystem to implement dynamic selection (during rendering of a singleprogram, or a sequence of different programs) of a sequence of differentsubsets of the objects (object channels) included in the program (e.g.,a first subset of objects indicative of one team, automatically followedby a second subset of objects indicative of a second team upon the eventthat the second team makes a score and thus becomes the currentlywinning team). Thus, in some such embodiments, realtime events steer orinfluence which object channels are included in the rendered mix. Theplayback system (e.g., object processing subsystem 22 of the FIG. 6system) may respond to metadata included in the program (e.g., metadatawhich indicates that at least one corresponding object is indicative ofa currently winning team, e.g., is indicative of crowd noise of theteam's fans or commentary of a radio announcer associated with thewinning team) to select which object channel(s) should be included inthe mix of speaker and object channels to be rendered. For example, thecontent creator may include (in an object based audio program) metadataindicative of a place order (or other hierarchy) of each of at leastsome audio object channels of the program (e.g., indicative of whichobject channels correspond to the team or car currently in first place,which object channels correspond to the team or car in second place, andso on). The playback system may be configured to respond to suchmetadata by selecting and rendering only the object channel(s) whichsatisfy a user specified rule (e.g., the object channel(s) relating tothe team in “n”th place, as indicated by object related metadata of theprogram).

Examples of object related metadata regarding object channels of theinventive object based audio program include (but are not limited to):metadata indicative of detailed information about how to render anobject channel; dynamic temporal metadata (e.g., indicative of atrajectory for panning of an object, object size, gains, etc.); andmetadata for use by an AVR (or other device or system downstream fromdecoding and object processing subsystems of some implementations of theinventive system) to render an object channel (e.g., with knowledge ofthe organization of an available playback speaker array). Such metadatamay specify constraints on object location, gain, muting, or otherrendering parameters, and/or constraints on how objects interact withother objects (e.g., constraints on which additional objects may beselected given that a specific object is selected), and/or may specifydefault objects and/or default rendering parameters (to be used in theabsence of user selection of other objects and/or rendering parameters).

In some embodiments, at least some object related metadata (andoptionally also at least some of the object channels) of the inventiveobject based audio program are sent in a separate bitstream or othercontainer (e.g., as a side mix for which a user might need to pay extrato receive and/or use) from the program's bed of speaker channels andconventional metadata. Without access to such object related metadata(or object related metadata and object channels), a user could decodeand render the bed of speaker channels, but could not select audioobjects of the program and could not render audio objects of the programin a mix with the audio indicated by the speaker channel bed. Each frameof the inventive object based audio program may include audio content ofmultiple object channels and corresponding object related metadata.

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance withsome embodiments of the invention includes at least one bed of speakerchannels, at least one object channel, and metadata indicative of alayered graph (sometimes referred to as a layered “mix graph”)indicative of selectable mixes (e.g., all selectable mixes) of thespeaker channels and object channel(s). For example, the mix graph isindicative of each rule applicable to selection of subsets of thespeaker and object channels. Typically, an encoded audio bitstream isindicative of at least some (i.e., at least a part) of the program'saudio content (e.g., a bed of speaker channels and at least some of theprogram's object channels) and object related metadata (including themetadata indicative of the mix graph), and optionally also at least oneadditional encoded audio bitstream or file is indicative of some of theprogram's audio content and/or object related metadata.

The layered mix graph is indicative of nodes (each of which may beindicative of a selectable channel or set of channels, or a category ofselectable channels or set of channels) and connections between thenodes (e.g., control interfaces to the nodes and/or rules for selectingchannels), and includes essential data (a “base” layer) and optional(i.e., optionally omitted) data (at least one “extension” layer).Typically, the layered mix graph is included in one of the encoded audiobitstream(s) indicative of the program, and can be assessed by graphtraversal (implemented by a playback system, e.g., the end user'splayback system) to determine a default mix of channels and options formodifying the default mix.

Where the mix graph is representable as a tree graph, the base layer canbe a branch (or two or more branches) of the tree graph, and eachextension layer can be another branch (or another set of two or morebranches) of the tree graph. For example, one branch of the tree graph(indicated by the base layer) may be indicative of selectable channelsand sets of channels that are available to all end users, and anotherbranch of the tree graph (indicated by an extension layer) may beindicative of additional selectable channels and/or sets of channelsthat are available only to some end users (e.g., such an extension layermay be provided only to only end users authorized to use it). FIG. 9 isan example of a tree graph which includes object channel nodes (e.g.,nodes indicative of object channels N0, N1, N2, N3, N4, N5, and N6) andother elements of a mix graph.

Typically the base layer contains (is indicative of) the graph structureand control interfaces to the nodes of the graph (e.g., panning, andgain control interfaces). The base layer is necessary for mapping anyuser interaction to the decoding/rendering process.

Each extension layer contains (is indicative of) an extension to thebase layer. The extensions are not immediately necessary for mappinguser interaction to the decoding process and hence can be transmitted ata slower rate and/or delayed, or omitted.

In some embodiments, the base layer is included as metadata of anindependent substream of the program (e.g., is transmitted as metadataof the independent substream).

An object based audio program generated (or transmitted, stored,buffered, decoded, rendered, or otherwise processed) in accordance withsome embodiments of the invention includes at least one bed of speakerchannels, at least one object channel, and metadata indicative of a mixgraph (which may or may not be a layered mix graph) indicative ofselectable mixes (e.g., all selectable mixes) of the speaker channelsand the object channel(s). An encoded audio bitstream (e.g., a Dolby Eor E-AC-3 bitstream) is indicative of at least a portion of the program,and metadata indicative of the mix graph (and typically also theselectable object and/or speaker channels) is included in every frame ofthe bitstream (or in each frame of a subset of the frames of thebitstream). For example, each frame may include at least one metadatasegment and at least one audio data segment, and the mix graph may beincluded in at least one metadata segment of each frame. Each metadatasegment (which may be referred to as a “container”) may have a formatwhich includes a metadata segment header (and optionally also otherelements), and one or more metadata payloads following the metadatasegment header. Each metadata payload is itself identified by a payloadheader. The mix graph, if present in a metadata segment, is included inone of the metadata payloads of the metadata segment.

In some embodiments, an object based audio program generated (ortransmitted, stored, buffered, decoded, rendered, or otherwiseprocessed) in accordance with the invention includes at least two bedsof speaker channels, at least one object channel, and metadataindicative of a mix graph (which may or may not be a layered mix graph).The mix graph is indicative of selectable mixes of the speaker channelsand the object channel(s), and includes at least one “bed mix” node.Each “bed mix” node defines a predetermined mix of speaker channel beds,and thus indicates or implements a predetermined set of mixing rules(optionally with user-selectable parameters) for mixing speaker channelsof two or more speaker beds of the program.

Consider an example in which the audio program is associated with asoccer (football) game between Team A (the home team) and Team B in astadium, and includes a 5.1 speaker channel bed (determined bymicrophone feeds) for the whole crowd in the stadium, a stereo feed forthe portion of the crowd biased toward Team A (i.e., audio captured fromspectators seated in a section of the stadium primarily occupied by fansof Team A), and another stereo feed for the portion of the crowd biasedtoward Team B (i.e., audio captured from spectators seated in a sectionof the stadium primarily occupied by fans of Team B). It is possible tomix these three feeds (5.1 channel neutral bed, 2.0 channel “Team A”bed, and 2.0 channel “Team B” bed) on a mixing console to generate four5.1 speaker channel beds (which may be referred to as “fan zone” beds):unbiased, home biased (a mix of the neutral and Team A beds), awaybiased (a mix of the neutral and Team B beds), and opposite (the neutralbed, mixed with the Team A bed panned to one side of the room, and withthe Team B bed panned to the opposite side of room). However,transmitting the four mixed 5.1 channel beds is expensive in terms ofbitrate. Thus, an embodiment of the inventive bitstream includesmetadata specifying bed mixing rules (for mixing of speaker channelbeds, e.g., to generate the four noted mixed 5.1 channel beds) to beimplemented by a playback system (e.g., in the home of an end user)based on user mix selection(s), as well as the speaker channel bedswhich can be mixed according to the rules (e.g., the original 5.1channel bed and the two biased stereo speaker channel beds). In responseto a bed mix node of the mix graph, the playback system could present tothe user an option (e.g., displayed via a user interface implemented bycontroller 23 of the FIG. 6 system) to select one of the four notedmixed 5.1 channel beds. In response to user selection of this mixed 5.1channel bed, the playback system (e.g., subsystem 22 of the FIG. 6system) would generate the selected mix using the (unmixed) speakerchannel beds transmitted in the bitstream.

In some embodiments, the bed mixing rules contemplate the followingoperations (which may have predetermined parameters or user-selectableparameters):

bed “rotation” (i.e., panning a speaker channel bed to Left, Right,Front or Back). For example for creating the above-mentioned ‘opposite’mix, the stereo Team A bed would be rotated to the Left side of theplayback speaker array (L and R channels of the Team A bed are mapped toL and Ls channels of the playback system) and the stereo Team B bedwould be rotated to the Right side of the playback speaker array (L andR channels of the Team B bed are mapped to R and Rs channels of theplayback system). Thus, a user interface of the playback system mightpresent to an end user a choice of one of the four above-mentioned“unbiased,” “home biased,” “away biased” and “opposite” bed mixes, andupon user selection of the “opposite” bed mix, the playback system wouldimplement the appropriate bed rotation during rendering of the“opposite” bed mix; and

ducking (i.e., attenuating) of specific speaker channels (targetchannels) in a bed mix (typically, to make headroom). For example, inthe above-mentioned soccer game example, a user interface of theplayback system might present to an end user a choice of one of the fourabove-mentioned “unbiased,” “home biased,” “away biased” and “opposite”bed mixes, and in response to user selection of the “opposite” bed mix,the playback system might implement target ducking during rendering ofthe “opposite” bed mix by ducking (attenuating) each of the L, Ls, R,and Rs channels of the neutral 5.1 channel bed by a predetermined amount(specified by metadata in the bitstream) before mixing the attenuated5.1 channel bed with the stereo “Team A” and “Team B” beds to generatethe “opposite” bed mix.

In another class of embodiments, an object based audio program generated(or transmitted, stored, buffered, decoded, rendered, or otherwiseprocessed) in accordance with the invention includes substreams, and thesubstreams are indicative of at least one bed of speaker channels, atleast one object channel, and object related metadata. The objectrelated metadata includes “substream” metadata (indicative of substreamstructure of the program and/or the manner in which the substreamsshould be decoded) and typically also a mix graph indicative ofselectable mixes (e.g., all selectable mixes) of the speaker channelsand the object channel(s). The substream metadata may be indicative ofwhich substreams of the program should be decoded independently of othersubstreams of the program, and which substreams of the program should bedecoded in association with at least one other substream of the program.

For example, in some embodiments, an encoded audio bitstream isindicative of at least some (i.e., at least a part) of the program'saudio content (e.g., at least one bed of speaker channels and at leastsome of the program's object channels) and metadata (e.g., a mix graphand substream metadata, and optionally also other metadata), and atleast one additional encoded audio bitstream (or file) is indicative ofsome of the program's audio content and/or metadata. In the case thateach of the bitstreams is a Dolby E bitstream (or is encoded in a mannerconsistent with the SMPTE 337 format for carrying non-pcm data in anAES3 serial digital audio bitstream), the bitstreams can collectively beindicative of multiples of up to 8 channels of audio content, with eachbitstream carrying up to 8 channels of audio data and typically alsoincluding metadata. Each of the bitstreams can be considered a substreamof a combined bitstream indicative of all the audio data and metadatacarried by all the bitstreams.

For another example, in some embodiments, an encoded audio bitstream isindicative of multiple substreams of metadata (e.g., a mix graph andsubstream metadata, and optionally also other object related metadata)and audio content of at least one audio program. Typically, each of thesubstreams is indicative of one or more of the program's channels (andtypically also metadata). In some cases, multiple substreams of anencoded audio bitstream are indicative of audio content of several audioprograms, e.g., a “main” audio program (which may be a multichannelprogram) and at least one other audio program (e.g., a program which isa commentary on the main audio program).

An encoded audio bitstream which is indicative of at least one audioprogram necessarily includes at least one “independent” substream ofaudio content. The independent substream is indicative of at least onechannel of an audio program (e.g., the independent substream may beindicative of the five full range channels of a conventional 5.1 channelaudio program). Herein, this audio program is referred to as a “main”program.

In some cases, an encoded audio bitstream is indicative of two or moreaudio programs (a “main” program and at least one other audio program).In such cases, the bitstream includes two or more independentsubstreams: a first independent substream indicative of at least onechannel of the main program; and at least one other independentsubstream indicative of at least one channel of another audio program (aprogram distinct from the main program). Each independent bitstream canbe independently decoded, and a decoder could operate to decode only asubset (not all) of the independent substreams of an encoded bitstream.

Optionally, an encoded audio bitstream which is indicative of a mainprogram (and optionally also at least one other audio program) includesat least one “dependent” substream of audio content. Each dependentsubstream is associated with one independent substream of the bitstream,and is indicative of at least one additional channel of the program(e.g., the main program) whose content is indicated by the associatedindependent substream (i.e., the dependent substream is indicative of atleast one channel of a program which is not indicated by the associatedindependent substream, and the associated independent substream isindicative of at least one channel of the program).

In an example of an encoded bitstream which includes an independentsubstream (indicative of at least one channel of a main program), thebitstream also includes a dependent substream (associated with theindependent bitstream) which is indicative of one or more additionalspeaker channels of the main program. Such additional speaker channelsare additional to the main program channel(s) indicated by theindependent substream. For example, if the independent substream isindicative of standard format Left, Right, Center, Left Surround, RightSurround full range speaker channels of a 7.1 channel main program, thedependent substream may be indicative of the two other full rangespeaker channels of the main program.

In accordance with the E-AC-3 standard, a conventional E-AC-3 bitstreammust be indicative of at least one independent substream (e.g., a singleAC-3 bitstream), and may be indicative of up to eight independentsubstreams. Each independent substream of an E-AC-3 bitstream may beassociated with up to eight dependent substreams.

In an example embodiment (to be described with reference to FIG. 11), anobject based audio program includes at least one bed of speakerchannels, at least one object channel, and metadata. The metadataincludes “substream” metadata (indicative of substream structure ofaudio content of the program and/or the manner in which substreams ofaudio content of the program should be decoded) and typically also a mixgraph indicative of selectable mixes of the speaker channels and theobject channel(s). The audio program associated with a soccer game. Anencoded audio bitstream (e.g., an E-AC-3 bitstream) is indicative of theprogram's audio content and metadata. The audio content of the program(and thus of the bitstream) includes four independent substreams, asindicated in FIG. 11. One independent substream (labeled as substream“I0” in FIG. 11) is indicative of a 5.1 speaker channel bed indicativeof neutral crowd noise at the soccer game. Another independent substream(labeled as substream “I1” in FIG. 11) is indicative of a 2.0 channel“Team A” bed (“M crowd”) indicative of sound from the portion of thegame crowd biased toward one team (“Team A”), a 2.0 channel “Team B” bed(“LivP crowd”) indicative of sound from the portion of the game crowdbiased toward the other team (“Team B”), and a monophonic object channel(“Sky comm 1”) indicative of commentary on the game. A third independentsubstream (labeled as substream “I2” in FIG. 11) is indicative of objectchannel audio content (labeled “2/0 ball kick”) indicative of soundproduced by a game ball as it is struck by soccer game eventparticipants, and three object channels (“Sky comm 2,” “Man comm,” and“Liv Comm”) each indicative of a different commentary on the soccergame. The fourth independent substream (labeled as substream “I3” inFIG. 11) is indicative of an object channel (labeled “PA”) indicative ofsound produced by the stadium public address system at the soccer game,an object channel (labeled “Radio”) indicative of a radio broadcast ofthe soccer game, and an object channel (labeled “Goal Flash”) indicativeof scoring of a goal during the soccer game.

In the FIG. 11 example, substream I0 includes the mix graph for theprogram and metadata (“obj md”) including at least some of the substreammetadata and at least some object channel related metadata. Each ofsubstreams 11, 12, and 13 includes metadata (“obj md”) at least someobject channel related metadata and optionally at least some substreammetadata.

In the FIG. 11 example, substream metadata of the bitstream indicatesthat during decoding, coupling should be “off” between each pair of theindependent substreams (so that each independent substream is decodedindependently of the other independent substreams), and substreammetadata of the bitstream indicates the program channels within eachsubstream for which coupling should be “on” (so that these channels arenot decoded independently of each other) or “off” (so that thesechannels are decoded independently of each other). For example, thesubstream metadata indicates that coupling should be “on” internal toeach of the two stereo speaker channel beds (the 2.0 channel “Team A”bed and the 2.0 channel “Team B” bed) of substream I1 but disabledacross the speaker channel beds of substream I1 and between themonophonic object channel and each of the speaker channel beds ofsubstream I1 (to cause the monophonic object channel and the speakerchannel beds to be decoded independently of each other). Similarly, thesubstream metadata indicates that coupling should be “on” internal tothe 5.1 speaker channel bed of substream I0 (to cause the speakerchannels of this bed to be decoded in association with each other).

In some embodiments, speaker channels and object channels are included(“packed”) within substreams of an audio program in a manner appropriateto a mix graph of the program. For example, if the mix graph is a treegraph, all channels of one branch of the graph may be included withinone substream, and all channels of another branch of the graph may beincluded within another substream.

In a class of embodiments, the invention is a method for generating anobject based audio program, said method including the steps of:

determining a bed of speaker channels indicative of audio content of afirst subset of a set of audio signals indicative of captured audiocontent (e.g., the outputs of the microphones of the FIG. 8 system, orinput to subsystem 210 of the FIG. 10 system);

determining a set of object channels indicative of audio content of asecond subset of the set of audio signals;

generating object related metadata indicative of the object channels;and

generating the object based audio program, such that said object basedaudio program is indicative of the bed of speaker channels, the objectchannels, and the object related metadata, and is renderable to providesound perceived as a mix of first audio content indicated by the bed ofspeaker channels and second audio content indicated by a selected subsetof the object channels, such that the second audio content is perceivedas emitting from source locations determined by the selected subset ofthe object channels. Typically, at least some (i.e., at least a part) ofthe object related metadata is indicative of an identification of eachof at least some of the object channels, and/or at least some of theobject related metadata is indicative of a default subset of the set ofobject channels to be rendered in the absence of end user selection of asubset of the set of object channels. Some embodiments in the class alsoinclude the step of generating the set of audio signals, including bycapturing audio content (e.g., at a spectator event).

In another class of embodiments, the invention is a method of renderingaudio content determined by an object based audio program, wherein theprogram is indicative of a bed of speaker channels, a set of objectchannels, and object related metadata, said method including steps of:

(a) determining a selected subset of the set of object channels;

(b) rendering audio content determined by the object based audioprogram, including by determining a mix of first audio content indicatedby the bed of speaker channels and second audio content indicated by theselected subset of the object channels.

In some embodiments, the method is performed by a playback systemincluding a set of speakers, and (b) includes a step of: in response tothe mix of the first audio content and the second audio content,generating speaker feeds for driving the set of speakers to emit sound,wherein the sound includes object channel sound indicative of the secondaudio content, and the object channel sound is perceivable as emittingfrom apparent source locations determined by the selected subset of theobject channels. The bed of speaker channels may include a speakerchannel for each speaker in the set of speakers.

FIG. 10 is a block diagram of a system which implements an embodiment ofthe invention.

Object processing system (object processor) 200 of the FIG. 10 systemincludes metadata generation subsystem 210, mezzanine encoder 212, andemulation subsystem 211, coupled as shown. Metadata generation subsystem210 is coupled to receive captured audio streams (e.g., streamsindicative of sound captured by microphones positioned at a spectatorevent, and optionally also other audio streams), and configured toorganize (e.g., group) the audio streams from console 104 into a bed ofspeaker channels and a number of object channels and/or sets of objectchannels. Subsystem 210 is also configured to generate object relatedmetadata indicative of the object channels (and/or object channel sets).Encoder 212 is configured to encode the object channels (and/or objectchannel sets), objected related metadata, and the speaker channel bed asa mezzanine type object based audio program (e.g., an object based audioprogram encoded as a Dolby E bitstream).

Emulation subsystem 211 of object processor 200 is configured to render(and play on a set of studio monitor speakers) at least a selectedsubset of the object channels (and/or object channel sets) and thespeaker channel bed (including by using the object related metadata togenerate a mix indicative of the selected object channel(s) and speakerchannels) so that the played back sound can be monitored by theoperator(s) of subsystem 200.

Transcoder 202 of the FIG. 10 system includes mezzanine decodersubsystem (mezzanine decoder) 213, and encoder 214, coupled as shown.Mezzanine decoder 213 is coupled and configured to receive and decodethe mezzanine type object based audio program output from objectprocessor 200. The decoded output of decoder 213 is re-encoded byencoder 214 into a format suitable for broadcast. In one embodiment, theencoded object based audio program output from encoder 214 is an E-AC-3bitstream (and thus encoder 214 is labeled as “DD+ Encoder” in FIG. 10).In other embodiments, the encoded object based audio program output fromencoder 214 is an AC-3 bitstream or has some other format. The objectbased audio program output of transcoder 202 is broadcast (or otherwisedelivered) to a number of end users.

Decoder 204 is included in the playback system of one such end user.Decoder 204 includes decoder 215 and rendering subsystem (renderer) 216,coupled as shown. Decoder 215 accepts (receives or reads) and decodesthe object based audio program delivered from transcoder 202. If decoder215 is configured in accordance with a typical embodiment of theinvention, the output of decoder 215 in typical operation includes:streams of audio samples indicative of the program's bed of speakerchannels, and streams of audio samples indicative of object channels(e.g., user-selectable audio object channels) of the program andcorresponding streams of object related metadata. In one embodiment, theencoded object based audio program input to decoder 215 is an E-AC-3bitstream, and thus decoder 215 is labeled as “DD+ Decoder” in FIG. 10.

Renderer 216 of decoder 204 includes an object processing subsystemcoupled to receive (from decoder 215) decoded speaker channels, objectchannels, and object related metadata of the delivered program. Renderer216 also includes a rendering subsystem configured to render the audiocontent determined by the object processing subsystem, for playback byspeakers (not shown) of the playback system.

Typically, renderer 216′s object processing subsystem is configured tooutput to renderer 216′s rendering subsystem a selected subset of thefull set of object channels indicated by the program, and correspondingobject related metadata. Renderer 216′s object processing subsystem istypically also configured to pass through unchanged (to the renderingsubsystem) the decoded speaker channels from decoder 215. The objectchannel selection performed by the object processing subsystem isdetermined in accordance with an embodiment of the invention, e.g., byuser selection(s) and/or rules (e.g., indicative of conditions and/orconstraints) which renderer 216 has been programmed or otherwiseconfigured to implement.

Each of elements 200, 202, and 204 of FIG. 10 (and each of elements 104,106, 108, and 110 of FIG. 8) may be implemented as a hardware system.The inputs of such a hardware implementation of processor 200 (orprocessor 106) would typically be multichannel audio digital interface(“MADI”) inputs. Typically, processor 106 of FIG. 8, and each ofencoders 212 and 214 of FIG. 10, includes a frame buffer. Typically, theframe buffer is a buffer memory coupled to receive an encoded inputaudio bitstream, and in operation the buffer memory stores (e.g., in anon-transitory manner) at least one frame of the encoded audiobitstream, and a sequence of the frames of the encoded audio bitstreamis asserted from the buffer memory to a downstream device or system.Also typically, each of decoders 213 and 215 of FIG. 10 includes a framebuffer. Typically, this frame buffer is a buffer memory coupled toreceive an encoded input audio bitstream, and in operation the buffermemory stores (e.g., in a non-transitory manner) at least one frame ofthe encoded audio bitstream to be decoded by decoder 213 or 215.

Any of the components or elements of processor 106 of FIG. 8 (orsubsystems 200, 202, and/or 204 of FIG. 10) may be implemented as one ormore processes and/or one or more circuits (e.g., ASICs, FPGAs, or otherintegrated circuits), in hardware, software, or a combination ofhardware and software.

An aspect of the invention is an audio processing unit (APU) configuredto perform any embodiment of the inventive method. Examples of APUsinclude, but are not limited to encoders (e.g., transcoders), decoders,codecs, pre-processing systems (pre-processors), post-processing systems(post-processors), audio bitstream processing systems, and combinationsof such elements.

In a class of embodiments, the invention is an APU including a buffermemory (buffer) which stores (e.g., in a non-transitory manner) at leastone frame or other segment (including audio content of a bed of speakerchannels and of object channels, and object related metadata) of anobject based audio program which has been generated by any embodiment ofthe inventive method. For example, production unit 3 of FIG. 5 mayinclude buffer 3A, which stores (e.g., in a non-transitory manner) atleast one frame or other segment (including audio content of a bed ofspeaker channels and of object channels, and object related metadata) ofthe object based audio program generated by unit 3. For another example,decoder 7 of FIG. 5 may include buffer 7A, which stores (e.g., in anon-transitory manner) at least one frame or other segment (includingaudio content of a bed of speaker channels and of object channels, andobject related metadata) of the object based audio program deliveredfrom subsystem 5 to decoder 7.

Embodiments of the present invention may be implemented in hardware,firmware, or software, or a combination thereof (e.g., as a programmablelogic array). For example, subsystem 106 of FIG. 8, or the FIG. 7system, or all or some of elements 20, 22, 24, 25, 26, 29, 35, 31, and35 of the FIG. 6 system, or all or some of elements 200, 202, and 204 ofFIG. 10, may be implemented in appropriately programmed (or otherwiseconfigured) hardware or firmware, e.g., as a programmed general purposeprocessor, digital signal processor, or microprocessor. Unless otherwisespecified, the algorithms or processes included as part of the inventionare not inherently related to any particular computer or otherapparatus. In particular, various general-purpose machines may be usedwith programs written in accordance with the teachings herein, or it maybe more convenient to construct more specialized apparatus (e.g.,integrated circuits) to perform the required method steps. Thus, theinvention may be implemented in one or more computer programs executingon one or more programmable computer systems (e.g., an implementation ofall or some of elements 20, 22, 24, 25, 26, 29, 35, 31, and 35 of FIG.6), each comprising at least one processor, at least one data storagesystem (including volatile and non-volatile memory and/or storageelements), at least one input device or port, and at least one outputdevice or port. Program code is applied to input data to perform thefunctions described herein and generate output information. The outputinformation is applied to one or more output devices, in known fashion.

Each such program may be implemented in any desired computer language(including machine, assembly, or high level procedural, logical, orobject oriented programming languages) to communicate with a computersystem. In any case, the language may be a compiled or interpretedlanguage.

For example, when implemented by computer software instructionsequences, various functions and steps of embodiments of the inventionmay be implemented by multithreaded software instruction sequencesrunning in suitable digital signal processing hardware, in which casethe various devices, steps, and functions of the embodiments maycorrespond to portions of the software instructions.

Each such computer program is preferably stored on or downloaded to astorage media or device (e.g., solid state memory or media, or magneticor optical media) readable by a general or special purpose programmablecomputer, for configuring and operating the computer when the storagemedia or device is read by the computer system to perform the proceduresdescribed herein. The inventive system may also be implemented as acomputer-readable storage medium, configured with (i.e., storing) acomputer program, where the storage medium so configured causes acomputer system to operate in a specific and predefined manner toperform the functions described herein.

A number of embodiments of the invention have been described. It shouldbe understood that various modifications may be made without departingfrom the spirit and scope of the invention. Numerous modifications andvariations of the present invention are possible in light of the aboveteachings. It is to be understood that within the scope of the appendedclaims, the invention may be practiced otherwise than as specificallydescribed herein.

What is claimed is:
 1. A method of rendering audio content determined byan object based audio program, wherein the program includes at least onebed of speaker channels, a set of object channels, and object relatedmetadata, said method comprising: (a) determining a selected subset ofthe set of object channels; (b) providing a menu of selectable mixes ofaudio content, each of the selectable mixes being indicative of adifferent mix of audio content of one said bed of speaker channels andaudio content of a subset of the set of object channels, wherein atleast a part of the object related metadata is indicative of at leastone constraint or condition on which of the selectable mixes areincluded in the menu; (c) selecting one of the selectable mixes from themenu, thereby determining the selected subset of the set of objectchannels; and (d) rendering audio content determined by the object basedaudio program based on the object related metadata, and determining amix of first audio content based on the bed of speaker channels and theselected subset of the set of object channels.
 2. The method of claim 1,wherein at least a part of the object related metadata is indicative ofidentification of and relationship between each of the object channels,and said at least a part of the object related metadata determines theleast one constraint or condition on which of the selectable mixes areincluded in the menu.
 3. A system for rendering audio content determinedby an object based audio program, wherein the program includes at leastone bed of speaker channels, a set of object channels, and objectrelated metadata, said system comprising: a first subsystem configuredto determine a selected subset of the set of object channels; a secondsubsystem configured to provide a menu of selectable mixes of audiocontent, each of the selectable mixes being indicative of a differentmix of audio content of one said bed of speaker channels and audiocontent of a subset of the set of object channels, wherein at least apart of the object related metadata is indicative of at least oneconstraint or condition on which of the selectable mixes are included inthe menu; a third subsystem configured to select one of the selectablemixes from the menu, thereby determining the selected subset of the setof object channels; and a fourth subsystem configured to render audiocontent determined by the object based audio program based on the objectrelated metadata, and determine a mix of first audio content based onthe bed of speaker channels and the selected subset of the set of objectchannels.